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Sample records for nitrifying bacterial aggregates

  1. Microelectrode Measurements of the Activity Distribution in Nitrifying Bacterial Aggregates

    PubMed Central

    de Beer, D.; van den Heuvel, J. C.; Ottengraf, S. P. P.

    1993-01-01

    Microelectrodes for ammonium, oxygen, nitrate, and pH were used to study nitrifying aggregates grown in a fluidized-bed reactor. Local reactant fluxes and distribution of microbial activity could be determined from the microprofiles. The interfacial fluxes of the reactants closely reflected the stoichiometry of bacterial nitrification. Both ammonium consumption and nitrate production were localized in the outer shells, with a thickness of approximately 100 to 120 μm, of the aggregates. Under conditions in which ammonium and oxygen penetrated the whole aggregate, nitrification was restricted to this zone; oxygen was consumed in the central parts of the aggregates as well, probably because of oxidation of dead biomass. A sudden increase of the oxygen concentration to saturation (pure oxygen) was inhibitory to nitrification. The pH profiles showed acidification in the aggregates, but not to an inhibitory level. The distribution of activity was determined by the penetration depth of oxygen during aggregate development in the reactor. Mass transfer was significantly limited by the boundary layer surrounding the aggregates. Microelectrode measurements showed that the thickness of this layer was correlated with the diffusion coefficient of the species. Determination of the distribution of nitrifying activity required the use of ammonium or nitrate microelectrodes, whereas the use of oxygen microelectrodes alone would lead to erroneous results. Images PMID:16348875

  2. A quantitative measure of nitrifying bacterial growth.

    PubMed

    Pollard, Peter C

    2006-05-01

    Nitrifying bacteria convert ammonia (NH3) to nitrate (NO3-) in a nitrification reaction. Methods to quantitatively separate the growth rate of these important bacterial populations from that of the dominant heterotrophic bacteria are important to our understanding of the nitrification process. The changing concentration of ammonia is often used as an indirect measure of nitrification but ammonification processes generate ammonia and confound this approach while heterotrophs remove nitrate via denitrification. Molecular probe methods can tell us what proportion of the microbial community is nitrifying bacteria but not their growth rate. The technique proposed here was able to quantify the growth rate of the nitrifying bacterial populations amidst complex ecological processes. The method incubates [methyl-3H] thymidine with water samples in the presence and absence of an inhibitor of nitrification-thiourea. The radioactively labeled DNA in the growing bacteria was extracted. The rate of incorporation of the label into the dividing bacterial DNA was used to determine bacterial growth rate. Total bacterial community growth rates in full-scale and pilot-scale fixed-film nitrifying reactors and an activated sludge reactor were 2.1 x 10(8), 4.1 x 10(8) and 0.4 x 10(8)cell ml(-1)d(-1), respectively; the growth rate of autotrophic-nitrifying bacteria was 0.7 x 10(8), 2.6 x 10(8) and 0.01 x 10(8)cell ml(-1)d(-1), respectively. Autotrophic-nitrifying bacteria contributed 30% and 60% of the total bacterial community growth rate in the nitrifying reactors whereas only 2% was observed in the activated sludge reactor that was not designed to nitrify. The rates of ammonia loss from the nitrifying reactors corresponded to the rate of growth of the nitrifying bacteria. This method has the potential to more often identify factors that enhance or limit nitrifying processes in both engineered and natural aquatic environments.

  3. Assessment of bacterial community structure in nitrifying biofilm under inorganic carbon-sufficient and -limited conditions.

    PubMed

    Bae, Hyokwan; Chung, Yun-Chul; Yang, Heejeong; Lee, Changsoo; Aryapratama, Rio; Yoo, Young J; Lee, Seockheon

    2015-01-01

    In this work, nitrification and changes in the composition of the total bacterial community under inorganic carbon (IC)-limited conditions, in a nitrifying moving bed biofilm reactor, was investigated. A culture-independent analysis of cloning and sequencing based on the 16S rRNA gene was applied to quantify the bacterial diversity and to determine bacterial taxonomic assignment. IC concentrations had significant effects on the stability of ammonia-oxidation as indicated by the reduction of the nitrogen conversion rate with high NH4(+)-N loadings. The predominance of Nitrosomonas europaea was maintained in spite of changes in the IC concentration. In contrast, heterotrophic bacterial species contributed to a high bacterial diversity, and to a dynamic shift in the bacterial community structure, under IC-limited conditions. In this study, individual functions of heterotrophic bacteria were estimated based on taxonomic information. Possible key roles of coexisting heterotrophic bacteria are the assimilation of organic compounds of extracellular polymeric substances produced by nitrifiers, and biofilm formation by providing a filamentous structure and aggregation properties.

  4. Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria.

    PubMed

    Choi, Okkyoung; Das, Atreyee; Yu, Chang-Ping; Hu, Zhiqiang

    2010-12-15

    Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. © 2010 Wiley Periodicals, Inc.

  5. Overall bacterial community composition and abundance of nitrifiers and denitrifiers in a typical macrotidal estuary.

    PubMed

    Zhu, Weijing; Wang, Cheng; Sun, Faqian; Zhao, Liancheng; Dou, Wenjie; Mao, Zhihua; Wu, Weixiang

    2017-10-01

    Coupled nitrogen cycling processes can alleviate the negative effects of eutrophication caused by excessive nitrogen load in estuarine ecosystems. The abundance and diversity of nitrifiers and denitrifiers across different environmental gradients were examined in the sediment of Hangzhou Bay. Quantitative PCR and Pearson's correlation analyses suggested that the bacterial ammonia-oxidizers (AOB) were the dominant phylotypes capable of ammonia oxidation, while the nirS-encoding denitrifiers predominated in the denitrification process. Simultaneously, nitrite and pH were found to be the two major factors influencing amoA and nir gene abundances, and the distribution of bacterial communities. Moreover, the ratio of nirS/AOB amoA gene abundance showed negative correlation with nitrite concentration. Fluorescence in situ hybridization further demonstrated that AOB and acetate-denitrifying cells were closely connected and formed obvious aggregates in the sediment. Together, all these results provided us a preliminary insight for coupled nitrification-denitrification processes in the sediment of Hangzhou Bay. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Vertical distribution of nitrifying populations in bacterial biofilms from a full-scale nitrifying trickling filter.

    PubMed

    Lydmark, Pär; Lind, Magnus; Sörensson, Fred; Hermansson, Malte

    2006-11-01

    Cryosectioned biofilm from three depths (0.5, 3.0 and 6.0 m) in a full-scale nitrifying trickling filter (NTF) were studied using fluorescence in situ hybridization (FISH). A large number of sections were used to determine how the biofilm thickness, structure and community composition varied with depth along the ammonium concentration gradient in the NTF, and how the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were distributed vertically within the biofilm. Both the biofilm thickness and relative biomass content of the biofilm decreased with depth, along with structural differences such as void size and surface roughness. Four AOB populations were found, with two Nitrosomonas oligotropha populations dominating at all depths. A smaller population of Nitrosomonas europaea was present only at 0.5 m, while a population of Nitrosomonas communis increased with depth. The two N. oligotropha populations showed different vertical distribution patterns within the biofilm, indicating different ecophysiologies even though they belong to the same AOB lineage. All NOB were identified as Nitrospira sp., and were generally more associated with the biofilm base than the surface-associated dominating AOB population. Additionally, a small population of anaerobic ammonia-oxidizers was found at 6.0 m, even though the biofilm was well aerated.

  7. p-Cresol mineralization and bacterial population dynamics in a nitrifying sequential batch reactor.

    PubMed

    Silva, Carlos David; Beristain-Montiel, Lizeth; de Maria Cuervo-López, Flor; Texier, Anne-Claire

    2014-09-01

    The ability of a nitrifying sludge to oxidize p-cresol was evaluated in a sequential batch reactor (SBR). p-Cresol was first transformed to p-hydroxybenzaldehyde and p-hydroxybenzoate, which were later mineralized. The specific rates of p-cresol consumption increased throughout the cycles. The bacterial population dynamics were monitored by using denaturing gradient gel electrophoresis (DGGE) and sequencing of DGGE fragments. The ability of the sludge to consume p-cresol and intermediates might be related to the presence of species such as Variovorax paradoxus and Thauera mechernichensis. p-Cresol (25 to 200mgC/L) did not affect the nitrifying SBR performance (ammonium consumption efficiency and nitrate production yield were close to 100% and 1, respectively). This may be related to the high stability observed in the nitrifying communities. It was shown that a nitrifying SBR may be a good alternative to eliminate simultaneously ammonium and p-cresol, maintaining stable the respiratory process as the bacterial community.

  8. 454 pyrosequencing-based characterization of the bacterial consortia in a well established nitrifying reactor.

    PubMed

    Ramirez-Vargas, Rocio; Serrano-Silva, Nancy; Navarro-Noya, Yendi E; Alcántara-Hernández, Rocio J; Luna-Guido, Marco; Thalasso, Frederic; Dendooven, Luc

    2015-01-01

    This present study aimed to characterize the bacterial community in a well-established nitrifying reactor by high-throughput sequencing of 16S rRNA amplicons. The laboratory-scale continuous stirred tank reactor has been supplied with ammonium (NH(4)(+)) as sole energy source for over 5 years, while no organic carbon has been added, assembling thus a unique planktonic community with a mean NH(4)(+) removal rate of 86 ± 1.4 mg NH(4)(+)-N/(L d). Results showed a nitrifying community composed of bacteria belonging to Nitrosomonas (relative abundance 11.0%) as the sole ammonia oxidizers (AOB) and Nitrobacter (9.3%) as the sole nitrite oxidizers (NOB). The Alphaproteobacteria (42.3% including Nitrobacter) were the most abundant class within the Proteobacteria (62.8%) followed by the Gammaproteobacteria (9.4%). However, the Betaproteobacteria (excluding AOB) contributed only 0.08%, confirming that Alpha- and Gammaproteobacteria thrived in low-organic-load environments while heterotrophic Betaproteobacteria are not well adapted to these conditions. Bacteroidetes, known to metabolize extracellular polymeric substances produced by nitrifying bacteria and secondary metabolites of the decayed biomass, was the second most abundant phylum (30.8%). It was found that Nitrosomonas and Nitrobacter sustained a broad population of heterotrophs in the reactor dominated by Alpha- and Gammaproteobacteria and Bacteroidetes, in a 1:4 ratio of total nitrifiers to all heterotrophs.

  9. Quantification of nitrifying bacterial populations in a full-scale nitrifying trickling filter using fluorescent in situ hybridization.

    PubMed

    Biesterfeld, S; Figueroa, L; Hernandez, M; Russell, P

    2001-01-01

    Fluorescent in situ hybridization (FISH) was used to quantify the ammonia-oxidizing populations within intact biofilm samples collected from a full-scale nitrifying trickling filter (NTF). Ammonia, nitrite, and nitrate concentrations were measured for aqueous samples taken in conjunction with biofilm samples at multiple filter depths. Correlation coefficients for individual sampling events, calculated by simple linear regression of FISH signal area and ammonia removal rates, ranged from 0.558 when using probe NEU23a to 0.982 when using probe Nso190. The improved correlations with Nso190 suggest that genera other than Nitrosomonas are present in this system. Percent biofilm coverage, as determined by 4',6-diamidino-2-phenylindole counterstaining and dry weight biomass measurements, did not change throughout the NTF. This indicates that biofilm growth is fairly uniform throughout the filter even if nitrifier growth is not.

  10. Influence of growth manner on nitrifying bacterial communities and nitrification kinetics in three lab-scale bioreactors.

    PubMed

    Wang, Feng; Liu, Yi; Wang, Jinghan; Zhang, Yalei; Yang, Haizhen

    2012-04-01

    The effects of growth type, including attached growth, suspended growth, and combined growth, on the characteristics of communities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were studied in three lab-scale Anaerobic/Anoxic(m)-Oxic(n) (AmOn) systems. These systems amplified activated sludge, biofilms, and a mixture of activated sludge and biofilm (AS-BF). Identical inocula were adopted to analyze the selective effects of mixed growth patterns on nitrifying bacteria. Fluctuations in the concentration of nitrifying bacteria over the 120 days of system operation were analyzed, as was the composition of nitrifying bacterial community in the stabilized stage. Analysis was conducted using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR. According to the DGGE patterns, the primary AOB lineages were Nitrosomonas europaea (six sequences), Nitrosomonas oligotropha (two sequences), and Nitrosospira (one sequence). The primary subclass of NOB community was Nitrospira, in which all identified sequences belonged to Nitrospira moscoviensis (14 sequences). Nitrobacter consisted of two lineages, namely Nitrobacter vulgaris (three sequences) and Nitrobacter alkalicus (two sequences). Under identical operating conditions, the composition of nitrifying bacterial communities in the AS-BF system demonstrated significant differences from those in the activated sludge system and those in the biofilm system. Major varieties included several new, dominant bacterial sequences in the AS-BF system, such as N. europaea and Nitrosospira and a higher concentration of AOB relative to the activated sludge system. However, no similar differences were discovered for the concentration of the NOB population. A kinetic study of nitrification demonstrated a higher maximum specific growth rate of mixed sludge and a lower half-saturation constant of mixed biofilm, indicating that the AS-BF system maintained relatively good

  11. Novel application of nitrifying bacterial consortia to ease ammonia toxicity in ornamental fish transport units: trials with zebrafish.

    PubMed

    Dhanasiri, A K S; Kiron, V; Fernandes, J M O; Bergh, O; Powell, M D

    2011-08-01

    To evaluate whether two commercial nitrifying bacterial consortia can function as biocontrol agents in ornamental fish transporting systems. The consortia were applied in a simulated set-up using zebrafish as the model organism in three trials. The efficacy of the bacterial consortia in controlling the ammonia level was validated by measuring water quality parameters such as total ammonia, nitrate and pH of the transport water. The bacterial community structure in the transport unit was studied using denaturing gradient gel electrophoresis. The consortia tested improved the nitrifying activity that in turn facilitated the reduction of ammonia that had accumulated during the transport. Bacterial profiles revealed the presence of both ammonia-oxidizing and nitrite-oxidizing bacteria in the transport bags. The application of the consortia during the transportation of zebrafish could profoundly improve the water quality by curbing ammonia accumulation. The potential of applying nitrifying bacteria as a bioremediation practice during the transport of ornamental fish has been demonstrated and this innovative approach contributes to the amelioration of current fish welfare in ornamental fish trade. © 2011 The Authors. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

  12. Effects of Aeration Cycles on Nitrifying Bacterial Populations and Nitrogen Removal in Intermittently Aerated Reactors

    PubMed Central

    Mota, Cesar; Head, Melanie A.; Ridenoure, Jennifer A.; Cheng, Jay J.; de los Reyes, Francis L.

    2005-01-01

    The effects of the lengths of aeration and nonaeration periods on nitrogen removal and the nitrifying bacterial community structure were assessed in intermittently aerated (IA) reactors treating digested swine wastewater. Five IA reactors were operated in parallel with different aeration-to-nonaeration time ratios (ANA). Populations of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were monitored using 16S rRNA slot blot hybridizations. AOB species diversity was assessed using amoA gene denaturant gradient gel electrophoresis. Nitrosomonas and Nitrosococcus mobilis were the dominant AOB and Nitrospira spp. were the dominant NOB in all reactors, although Nitrosospira and Nitrobacter were also detected at lower levels. Reactors operated with the shortest aeration time (30 min) showed the highest Nitrosospira rRNA levels, and reactors operated with the longest anoxic periods (3 and 4 h) showed the lowest levels of Nitrobacter, compared to the other reactors. Nitrosomonas sp. strain Nm107 was detected in all reactors, regardless of the reactor's performance. Close relatives of Nitrosomonas europaea, Nitrosomonas sp. strain ENI-11, and Nitrosospira multiformis were occasionally detected in all reactors. Biomass fractions of AOB and effluent ammonia concentrations were not significantly different among the reactors. NOB were more sensitive than AOB to long nonaeration periods, as nitrite accumulation and lower total NOB rRNA levels were observed for an ANA of 1 h:4 h. The reactor with the longest nonaeration time of 4 h performed partial nitrification, followed by denitrification via nitrite, whereas the other reactors removed nitrogen through traditional nitrification and denitrification via nitrate. Superior ammonia removal efficiencies were not associated with levels of specific AOB species or with higher AOB species diversity. PMID:16332848

  13. Protein Aggregation Profile of the Bacterial Cytosol

    PubMed Central

    de Groot, Natalia S.; Ventura, Salvador

    2010-01-01

    Background Protein misfolding is usually deleterious for the cell, either as a consequence of the loss of protein function or the buildup of insoluble and toxic aggregates. The aggregation behavior of a given polypeptide is strongly influenced by the intrinsic properties encoded in its sequence. This has allowed the development of effective computational methods to predict protein aggregation propensity. Methodology/Principal Findings Here, we use the AGGRESCAN algorithm to approximate the aggregation profile of an experimental cytosolic Escherichia coli proteome. The analysis indicates that the aggregation propensity of bacterial proteins is associated with their length, conformation, location, function, and abundance. The data are consistent with the predictions of other algorithms on different theoretical proteomes. Conclusions/Significance Overall, the study suggests that the avoidance of protein aggregation in functional environments acts as a strong evolutionary constraint on polypeptide sequences in both prokaryotic and eukaryotic organisms. PMID:20195530

  14. Oxygen limitation within a bacterial aggregate.

    PubMed

    Wessel, Aimee K; Arshad, Talha A; Fitzpatrick, Mignon; Connell, Jodi L; Bonnecaze, Roger T; Shear, Jason B; Whiteley, Marvin

    2014-04-15

    ABSTRACT Cells within biofilms exhibit physiological heterogeneity, in part because of chemical gradients existing within these spatially structured communities. Previous work has examined how chemical gradients develop in large biofilms containing >10(8) cells. However, many bacterial communities in nature are composed of small, densely packed aggregates of cells (≤ 10(5) bacteria). Using a gelatin-based three-dimensional (3D) printing strategy, we confined the bacterium Pseudomonas aeruginosa within picoliter-sized 3D "microtraps" that are permeable to nutrients, waste products, and other bioactive small molecules. We show that as a single bacterium grows into a maximally dense (10(12) cells ml(-1)) clonal population, a localized depletion of oxygen develops when it reaches a critical aggregate size of ~55 pl. Collectively, these data demonstrate that chemical and phenotypic heterogeneity exists on the micrometer scale within small aggregate populations. IMPORTANCE Before developing into large, complex communities, microbes initially cluster into aggregates, and it is unclear if chemical heterogeneity exists in these ubiquitous micrometer-scale aggregates. We chose to examine oxygen availability within an aggregate since oxygen concentration impacts a number of important bacterial processes, including metabolism, social behaviors, virulence, and antibiotic resistance. By determining that oxygen availability can vary within aggregates containing ≤ 10(5) bacteria, we establish that physiological heterogeneity exists within P. aeruginosa aggregates, suggesting that such heterogeneity frequently exists in many naturally occurring small populations.

  15. Impact of Short-Term Acidification on Nitrification and Nitrifying Bacterial Community Dynamics in Soilless Cultivation Media

    PubMed Central

    Levkovitch, Irit; Negreanu, Yael; Dowd, Scot; Frenk, Sammy; Silber, Avner

    2012-01-01

    Soilless medium-based horticulture systems are highly prevalent due to their capacity to optimize growth of high-cash crops. However, these systems are highly dynamic and more sensitive to physiochemical and pH perturbations than traditional soil-based systems, especially during nitrification associated with ammonia-based fertilization. The objective of this study was to assess the impact of nitrification-generated acidification on ammonia oxidation rates and nitrifying bacterial community dynamics in soilless growth media. To achieve this goal, perlite soilless growth medium from a commercial bell pepper greenhouse was incubated with ammonium in bench-scale microcosm experiments. Initial quantitative real-time PCR analysis indicated that betaproteobacterial ammonia oxidizers were significantly more abundant than ammonia-oxidizing archaea, and therefore, research focused on this group. Ammonia oxidation rates were highest between 0 and 9 days, when pH values dropped from 7.4 to 4.9. Pyrosequencing of betaproteobacterial ammonia-oxidizing amoA gene fragments indicated that r-strategist-like Nitrosomonas was the dominant ammonia-oxidizing bacterial genus during this period, seemingly due to the high ammonium concentration and optimal growth conditions in the soilless media. Reduction of pH to levels below 4.8 resulted in a significant decrease in both ammonia oxidation rates and the diversity of ammonia-oxidizing bacteria, with increased relative abundance of the r-strategist-like Nitrosospira. Nitrite oxidizers (Nitrospira and Nitrobacter) were on the whole more abundant and less sensitive to acidification than ammonia oxidizers. This study demonstrates that nitrification and nitrifying bacterial community dynamics in high-N-load intensive soilless growth media may be significantly different from those in in-terra agricultural systems. PMID:22773643

  16. Antibiotics promote aggregation within aquatic bacterial communities

    PubMed Central

    Corno, Gianluca; Coci, Manuela; Giardina, Marco; Plechuk, Sonia; Campanile, Floriana; Stefani, Stefania

    2014-01-01

    The release of antibiotics (AB) into the environment poses several threats for human health due to potential development of AB-resistant natural bacteria. Even though the use of low-dose antibiotics has been promoted in health care and farming, significant amounts of AB are observed in aquatic environments. Knowledge on the impact of AB on natural bacterial communities is missing both in terms of spread and evolution of resistance mechanisms, and of modifications of community composition and productivity. New approaches are required to study the response of microbial communities rather than individual resistance genes. In this study a chemostat-based experiment with 4 coexisting bacterial strains has been performed to mimicking the response of a freshwater bacterial community to the presence of antibiotics in low and high doses. Bacterial abundance rapidly decreased by 75% in the presence of AB, independently of their concentration, and remained constant until the end of the experiment. The bacterial community was mainly dominated by Aeromonas hydrophila and Brevundimonas intermedia while the other two strains, Micrococcus luteus and Rhodococcus sp. never exceed 10%. Interestingly, the bacterial strains, which were isolated at the end of the experiment, were not AB-resistant, while reassembled communities composed of the 4 strains, isolated from treatments under AB stress, significantly raised their performance (growth rate, abundance) in the presence of AB compared to the communities reassembled with strains isolated from the treatment without AB. By investigating the phenotypic adaptations of the communities subjected to the different treatments, we found that the presence of AB significantly increased co-aggregation by 5–6 fold. These results represent the first observation of co-aggregation as a successful strategy of AB resistance based on phenotype in aquatic bacterial communities, and can represent a fundamental step in the understanding of the effects of

  17. Monitoring structure and activity of nitrifying bacterial biofilm in an automatic biodetector of water toxicity.

    PubMed

    Woznica, Andrzej; Nowak, Agnieszka; Beimfohr, Claudia; Karczewski, Jerzy; Bernas, Tytus

    2010-02-01

    Automatic biodetector of water toxicity is a biosensor based on monitoring of catalytic activity of the nitrifying bacteria. To create a standardized biosensing system, development of the biofilm must be characterized to determine the prerequisites for its biological (biocatalytic) stability. In this paper, growth of biofilm comprising ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the open cellular polyurethane material polyurethane sponge bioreactor has been investigated. Dynamics of the biofilm formation was estimated using AOB and NOB metabolic activity and the volume occupied by these two types of bacteria in the biofilm. Spectrophotometry liquid ion chromatography and image cytometry were used, respectively, for these measurements. A mathematical model of the dynamics of biofilm formation was established. These data indicate that open cellular polyurethane material is a good basis for the immobilization of nitrifying bacteria. Moreover, growth of the biofilm leads to its stable structural form, whose biocatalytic activity (12.29 for AOB and 6.84 micromol min(-1) for NOB) is constant in the long term. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  18. Nitrifying bacterial communities in an aquaculture wastewater treatment system using fluorescence in situ hybridization (FISH), 16S rRNA gene cloning, and phylogenetic analysis.

    PubMed

    Paungfoo, Chanyarat; Prasertsan, Poonsuk; Burrell, Paul C; Intrasungkha, Nugul; Blackall, Linda L

    2007-07-01

    Aquaculture, especially shrimp farming, has played a major role in the growth of Thailand's economy in recent years, as well as in many South East Asian countries. However, the nutrient discharges from these activities have caused adverse impacts on the quality of the receiving waterways. In particular nitrogenous compounds, which may accumulate in aquaculture ponds, can be toxic to aquatic animals and cause environmental problems such as eutrophication. The mineralization process is well known, but certain aspects of the microbial ecology of nitrifiers, the microorganisms that convert ammonia to nitrate, are poorly understood. A previously reported enrichment of nitrifying bacteria (ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) from a shrimp farm inoculated in a sequencing batch reactor (SBR) was studied by molecular methods. The initial identification and partial quantification of the nitrifying bacteria (AOB and NOB) were carried out by fluorescence in situ hybridization (FISH) using previously published 16S rRNA-targeting oligonucleotide probes. The two dominant bacterial groups detected by FISH were from the Cytophaga-Flavobacterium-Bacteroides and Proteobacteria (beta subdivision) phyla. Published FISH probes for Nitrobacter and Nitrospira did not hybridize to any of the bacterial cells. Therefore it is likely that new communities of NOBs, differing from previously reported ones, exist in the enrichments. Molecular genetic techniques (cloning, sequencing, and phylogenetic analysis) targeting the 16S rRNA genes from the nitrifying enrichments were performed to identify putative AOBs and NOBs.

  19. Characterization of nitrifying, denitrifying, and overall bacterial communities in permeable marine sediments of the northeastern Gulf of Mexico.

    PubMed

    Mills, Heath J; Hunter, Evan; Humphrys, Mike; Kerkhof, Lee; McGuinness, Lora; Huettel, Markus; Kostka, Joel E

    2008-07-01

    Sandy or permeable sediment deposits cover the majority of the shallow ocean seafloor, and yet the associated bacterial communities remain poorly described. The objective of this study was to expand the characterization of bacterial community diversity in permeable sediment impacted by advective pore water exchange and to assess effects of spatial, temporal, hydrodynamic, and geochemical gradients. Terminal restriction fragment length polymorphism (TRFLP) was used to analyze nearly 100 sediment samples collected from two northeastern Gulf of Mexico subtidal sites that primarily differed in their hydrodynamic conditions. Communities were described across multiple taxonomic levels using universal bacterial small subunit (SSU) rRNA targets (RNA- and DNA-based) and functional markers for nitrification (amoA) and denitrification (nosZ). Clonal analysis of SSU rRNA targets identified several taxa not previously detected in sandy sediments (i.e., Acidobacteria, Actinobacteria, Chloroflexi, Cyanobacteria, and Firmicutes). Sequence diversity was high among the overall bacterial and denitrifying communities, with members of the Alphaproteobacteria predominant in both. Diversity of bacterial nitrifiers (amoA) remained comparatively low and did not covary with the other gene targets. TRFLP fingerprinting revealed changes in sequence diversity from the family to species level across sediment depth and study site. The high diversity of facultative denitrifiers was consistent with the high permeability, deeper oxygen penetration, and high rates of aerobic respiration determined in these sediments. The high relative abundance of Gammaproteobacteria in RNA clone libraries suggests that this group may be poised to respond to short-term periodic pulses of growth substrates, and this observation warrants further investigation.

  20. Abundance and diversity of bacterial nitrifiers and denitrifiers and their functional genes in tannery wastewater treatment plants revealed by high-throughput sequencing.

    PubMed

    Wang, Zhu; Zhang, Xu-Xiang; Lu, Xin; Liu, Bo; Li, Yan; Long, Chao; Li, Aimin

    2014-01-01

    Biological nitrification/denitrification is frequently used to remove nitrogen from tannery wastewater containing high concentrations of ammonia. However, information is limited about the bacterial nitrifiers and denitrifiers and their functional genes in tannery wastewater treatment plants (WWTPs) due to the low-throughput of the previously used methods. In this study, 454 pyrosequencing and Illumina high-throughput sequencing, combined with molecular methods, were used to comprehensively characterize structures and functions of nitrification and denitrification bacterial communities in aerobic and anaerobic sludge of two full-scale tannery WWTPs. Pyrosequencing of 16S rRNA genes showed that Proteobacteria and Synergistetes dominated in the aerobic and anaerobic sludge, respectively. Ammonia-oxidizing bacteria (AOB) amoA gene cloning revealed that Nitrosomonas europaea dominated the ammonia-oxidizing community in the WWTPs. Metagenomic analysis showed that the denitrifiers mainly included the genera of Thauera, Paracoccus, Hyphomicrobium, Comamonas and Azoarcus, which may greatly contribute to the nitrogen removal in the two WWTPs. It is interesting that AOB and ammonia-oxidizing archaea had low abundance although both WWTPs demonstrated high ammonium removal efficiency. Good correlation between the qPCR and metagenomic analysis is observed for the quantification of functional genes amoA, nirK, nirS and nosZ, indicating that the metagenomic approach may be a promising method used to comprehensively investigate the abundance of functional genes of nitrifiers and denitrifiers in the environment.

  1. Investigation of Archaeal and Bacterial community structure of five different small drinking water networks with special regard to the nitrifying microorganisms.

    PubMed

    Nagymáté, Zsuzsanna; Homonnay, Zalán G; Márialigeti, Károly

    2016-01-01

    Total microbial community structure, and particularly nitrifying communities inhabiting five different small drinking water networks characterized with different water physical and chemical parameters was investigated, using cultivation-based methods and sequence aided Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis. Ammonium ion, originated from well water, was only partially oxidized via nitrite to nitrate in the drinking water distribution systems. Nitrification occurred at low ammonium ion concentration (27-46μM), relatively high pH (7.6-8.2) and over a wide range of dissolved oxygen concentrations (0.4-9.0mgL(-1)). The nitrifying communities of the distribution systems were characterized by variable most probable numbers (2×10(2)-7.1×10(4) MPN L(-1)) and probably originated from the non-treated well water. The sequence aided T-RFLP method revealed that ammonia-oxidizing microorganisms and nitrite-oxidizing Bacteria (Nitrosomonas oligotropha, Nitrosopumilus maritimus, and Nitrospira moscoviensis, 'Candidatus Nitrospira defluvii') were present in different ratios in the total microbial communities of the distinct parts of the water network systems. The nitrate generated by nitrification was partly utilized by nitrate-reducing (and denitrifying) Bacteria, present in low MPN and characterized by sequence aided T-RFLP as Comamonas sp. and Pseudomonas spp. Different environmental factors, like pH, chemical oxygen demand, calculated total inorganic nitrogen content (moreover nitrite and nitrate concentration), temperature had important effect on the total bacterial and archaeal community distribution.

  2. Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira.

    PubMed

    Bartelme, Ryan P; McLellan, Sandra L; Newton, Ryan J

    2017-01-01

    Recirculating aquaculture systems (RAS) are unique engineered ecosystems that minimize environmental perturbation by reducing nutrient pollution discharge. RAS typically employ a biofilter to control ammonia levels produced as a byproduct of fish protein catabolism. Nitrosomonas (ammonia-oxidizing), Nitrospira, and Nitrobacter (nitrite-oxidizing) species are thought to be the primary nitrifiers present in RAS biofilters. We explored this assertion by characterizing the biofilter bacterial and archaeal community of a commercial scale freshwater RAS that has been in operation for >15 years. We found the biofilter community harbored a diverse array of bacterial taxa (>1000 genus-level taxon assignments) dominated by Chitinophagaceae (~12%) and Acidobacteria (~9%). The bacterial community exhibited significant composition shifts with changes in biofilter depth and in conjunction with operational changes across a fish rearing cycle. Archaea also were abundant, and were comprised solely of a low diversity assemblage of Thaumarchaeota (>95%), thought to be ammonia-oxidizing archaea (AOA) from the presence of AOA ammonia monooxygenase genes. Nitrosomonas were present at all depths and time points. However, their abundance was >3 orders of magnitude less than AOA and exhibited significant depth-time variability not observed for AOA. Phylogenetic analysis of the nitrite oxidoreductase beta subunit (nxrB) gene indicated two distinct Nitrospira populations were present, while Nitrobacter were not detected. Subsequent identification of Nitrospira ammonia monooxygenase alpha subunit genes in conjunction with the phylogenetic placement and quantification of the nxrB genotypes suggests complete ammonia-oxidizing (comammox) and nitrite-oxidizing Nitrospira populations co-exist with relatively equivalent and stable abundances in this system. It appears RAS biofilters harbor complex microbial communities whose composition can be affected directly by typical system operations while

  3. Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira

    PubMed Central

    Bartelme, Ryan P.; McLellan, Sandra L.; Newton, Ryan J.

    2017-01-01

    Recirculating aquaculture systems (RAS) are unique engineered ecosystems that minimize environmental perturbation by reducing nutrient pollution discharge. RAS typically employ a biofilter to control ammonia levels produced as a byproduct of fish protein catabolism. Nitrosomonas (ammonia-oxidizing), Nitrospira, and Nitrobacter (nitrite-oxidizing) species are thought to be the primary nitrifiers present in RAS biofilters. We explored this assertion by characterizing the biofilter bacterial and archaeal community of a commercial scale freshwater RAS that has been in operation for >15 years. We found the biofilter community harbored a diverse array of bacterial taxa (>1000 genus-level taxon assignments) dominated by Chitinophagaceae (~12%) and Acidobacteria (~9%). The bacterial community exhibited significant composition shifts with changes in biofilter depth and in conjunction with operational changes across a fish rearing cycle. Archaea also were abundant, and were comprised solely of a low diversity assemblage of Thaumarchaeota (>95%), thought to be ammonia-oxidizing archaea (AOA) from the presence of AOA ammonia monooxygenase genes. Nitrosomonas were present at all depths and time points. However, their abundance was >3 orders of magnitude less than AOA and exhibited significant depth-time variability not observed for AOA. Phylogenetic analysis of the nitrite oxidoreductase beta subunit (nxrB) gene indicated two distinct Nitrospira populations were present, while Nitrobacter were not detected. Subsequent identification of Nitrospira ammonia monooxygenase alpha subunit genes in conjunction with the phylogenetic placement and quantification of the nxrB genotypes suggests complete ammonia-oxidizing (comammox) and nitrite-oxidizing Nitrospira populations co-exist with relatively equivalent and stable abundances in this system. It appears RAS biofilters harbor complex microbial communities whose composition can be affected directly by typical system operations while

  4. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates

    PubMed Central

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P.; Gordon, Vernita D.; Allen, Rosalind J.

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities. PMID:26934187

  5. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates.

    PubMed

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P; Gordon, Vernita D; Allen, Rosalind J

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities.

  6. Copper Complex in Poly(vinyl chloride) as a Nitric Oxide-Generating Catalyst for the Control of Nitrifying Bacterial Biofilms.

    PubMed

    Wonoputri, Vita; Gunawan, Cindy; Liu, Sanly; Barraud, Nicolas; Yee, Lachlan H; Lim, May; Amal, Rose

    2015-10-14

    In this study, catalytic generation of nitric oxide by a copper(II) complex embedded within a poly(vinyl chloride) matrix in the presence of nitrite (source of nitric oxide) and ascorbic acid (reducing agent) was shown to effectively control the formation and dispersion of nitrifying bacteria biofilms. Amperometric measurements indicated increased and prolonged generation of nitric oxide with the addition of the copper complex when compared to that with nitrite and ascorbic acid alone. The effectiveness of the copper complex-nitrite-ascorbic acid system for biofilm control was quantified using protein analysis, which showed enhanced biofilm suppression when the copper complex was used in comparison to that with nitrite and ascorbic acid treatment alone. Confocal laser scanning microscopy (CLSM) and LIVE/DEAD staining revealed a reduction in cell surface coverage without a loss of viability with the copper complex and up to 5 mM of nitrite and ascorbic acid, suggesting that the nitric oxide generated from the system inhibits proliferation of the cells on surfaces. Induction of nitric oxide production by the copper complex system also triggered the dispersal of pre-established biofilms. However, the addition of a high concentration of nitrite and ascorbic acid to a pre-established biofilm induced bacterial membrane damage and strongly decreased the metabolic activity of planktonic and biofilm cells, as revealed by CLSM with LIVE/DEAD staining and intracellular adenosine triphosphate measurements, respectively. This study highlights the utility of the catalytic generation of nitric oxide for the long-term suppression and removal of nitrifying bacterial biofilms.

  7. Bacterial aggregation and biofilm formation in a vortical flow

    PubMed Central

    Yazdi, Shahrzad; Ardekani, Arezoo M.

    2012-01-01

    Bacterial aggregation and patchiness play an important role in a variety of ecological processes such as competition, adaptation, epidemics, and succession. Here, we demonstrate that hydrodynamics of their environment can lead to their aggregation. This is specially important since microbial habitats are rarely at rest (e.g., ocean, blood stream, flow in porous media, and flow through membrane filtration processes). In order to study the dynamics of bacterial collection in a vortical flow, we utilize a microfluidic system to mimic some of the important microbial conditions at ecologically relevant spatiotemporal scales. We experimentally demonstrate the formation of “ring”-shaped bacterial collection patterns and subsequently the formation of biofilm streamers in a microfluidic system. Acoustic streaming of a microbubble is used to generate a vortical flow in a microchannel. Due to bacteria's finite-size, the microorganisms are directed to closed streamlines and trapped in the vortical flow. The collection of bacteria in the vortices occurs in a matter of seconds, and unexpectedly, triggers the formation of biofilm streamers within minutes. Swimming bacteria have a competitive advantage to respond to their environmental conditions. In order to investigate the role of bacterial motility on the rate of collection, two strains of Escherichia coli bacteria with different motilities are used. We show that the bacterial collection in a vortical flow is strongly pronounced for high motile bacteria. PMID:24339847

  8. Microalgal-bacterial aggregates: Applications and perspectives for wastewater treatment.

    PubMed

    Quijano, Guillermo; Arcila, Juan S; Buitrón, Germán

    2017-11-01

    Research on wastewater treatment by means of microalgal-bacterial processes has become a hot topic worldwide during the last two decades. Owing to the lower energy demand for oxygenation, the enhanced nutrient removal and the potential for resource recovery, microalgal-based technologies are nowadays considered as a good alternative to conventional activated sludge treatments in many instances. Nevertheless, biomass harvesting still constitutes one of the major challenges of microalgal-bacterial systems for wastewater treatment, which is hindered by the poor settleability of microalgal biomass. In this review, the use of microalgal-bacterial aggregates (MABAs) to overcome harvesting issues and to enhance resource recovery is presented. The fundamentals of MABAs-based technologies, the operational strategies and factors affecting the formation of MABAs, the microbiology and the methanogenic potential of the aggregates are addressed and critically discussed. The most recent findings and the challenges facing this technology towards its consolidation are also presented. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Signaling factor interactions with polysaccharide aggregates of bacterial biofilms.

    PubMed

    DeSalvo, Stephen C; Liu, Yating; Choudhary, Geetika Sanjay; Ren, Dacheng; Nangia, Shikha; Sureshkumar, Radhakrishna

    2015-02-17

    Biofilms are surface-attached colonies of bacteria embedded in an extracellular polymeric substance (EPS). Inside the eukaryotic hosts, bacterial biofilms interact with the host cells through signaling factors (SFs). These signaling processes play important roles in the interaction between bacteria and host cells and the outcome of infections and symbiosis. However, how host immune factors diffuse through biofilms is not well understood. Here, we describe synergistic molecular dynamics and experimental approaches for studying the translocation of signaling factors through polysaccharide chain aggregates present in the extracellular matrix of bacterial biofilms. The effect of polysaccharide chain degradation on the energetics of SF-EPS interactions was examined by simulating an EPS consisting of various polysaccharide chain lengths. It is shown that the SF stabilization energy, defined as the average potential of mean force difference between the environments outside and within the matrix, increases linearly with decreasing chain length. This effect has been explained based on the changes in the polysaccharide configurations around the SF. Specifically, shorter chains are packed tightly around the SF, promoting favorable SF-EPS interactions, while longer chains are packed loosely resulting in screening of interactions with neighboring chains. We further investigated the translocation of SFs through the host cell membrane using molecular dynamics simulations. Further, simulations predict the existence of energy barriers greater than 1000 kJ mol(-1) associated with the translocation of the signaling factors necrosis factor-alpha (TNF-α) and granulocyte macrophage colony stimulating factor (GM-CSF) across the lipid bilayer. The agreement of computational and experimental findings motivates future computational studies using a more detailed description of the EPS aimed at understanding the role of the extracellular matrix on biofilm drug resistance.

  10. Nitrifying bacterial biomass and nitrification activity evaluated by FISH and an automatic on-line instrument at full-scale Fusina (Venice, Italy) WWTP.

    PubMed

    Badoer, S; Miana, P; Della Sala, S; Marchiori, G; Tandoi, V; Di Pippo, F

    2015-12-01

    In this study, monthly variations in biomass of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were analysed over a 1-year period by fluorescence in situ hybridization (FISH) at the full-scale Fusina WWTP. The nitrification capacity of the plant was also monitored using periodic respirometric batch tests and by an automated on-line titrimetric instrument (TITrimetric Automated ANalyser). The percentage of nitrifying bacteria in the plant was the highest in summer and was in the range of 10-15 % of the active biomass. The maximum nitrosation rate varied in the range 2.0-4.0 mg NH4 g(-1) VSS h(-1) (0.048-0.096 kg TKN kg(-1) VSS day(-1)): values obtained by laboratory measurements and the on-line instrument were similar and significantly correlated. The activity measurements provided a valuable tool for estimating the maximum total Kjeldahl nitrogen (TKN) loading possible at the plant and provided an early warning of whether the TKN was approaching its limiting value. The FISH analysis permitted determination of the nitrifying biomass present. The main operational parameter affecting both the population dynamics and the maximum nitrosation activity was mixed liquor volatile suspended solids (MLVSS) concentration and was negatively correlated with ammonia-oxidizing bacteria (AOB) (p = 0.029) and (NOB) (p = 0.01) abundances and positively correlated with maximum nitrosation rates (p = 0.035). Increases in concentrations led to decreases in nitrifying bacteria abundance, but their nitrosation activity was higher. These results demonstrate the importance of MLVSS concentration as key factor in the development and activity of nitrifying communities in wastewater treatment plants (WWTPs). Operational data on VSS and sludge volume index (SVI) values are also presented on 11-year basis observations.

  11. Mechanisms and rates of bacterial colonization of sinking aggregates.

    PubMed

    Kiørboe, Thomas; Grossart, Hans-Peter; Ploug, Helle; Tang, Kam

    2002-08-01

    Quantifying the rate at which bacteria colonize aggregates is a key to understanding microbial turnover of aggregates. We used encounter models based on random walk and advection-diffusion considerations to predict colonization rates from the bacteria's motility patterns (swimming speed, tumbling frequency, and turn angles) and the hydrodynamic environment (stationary versus sinking aggregates). We then experimentally tested the models with 10 strains of bacteria isolated from marine particles: two strains were nonmotile; the rest were swimming at 20 to 60 microm s(-1) with different tumbling frequency (0 to 2 s(-1)). The rates at which these bacteria colonized artificial aggregates (stationary and sinking) largely agreed with model predictions. We report several findings. (i) Motile bacteria rapidly colonize aggregates, whereas nonmotile bacteria do not. (ii) Flow enhances colonization rates. (iii) Tumbling strains colonize aggregates enriched with organic substrates faster than unenriched aggregates, while a nontumbling strain did not. (iv) Once on the aggregates, the bacteria may detach and typical residence time is about 3 h. Thus, there is a rapid exchange between attached and free bacteria. (v) With the motility patterns observed, freely swimming bacteria will encounter an aggregate in <1 day at typical upper-ocean aggregate concentrations. This is faster than even starving bacteria burn up their reserves, and bacteria may therefore rely solely on aggregates for food. (vi) The net result of colonization and detachment leads to a predicted equilibrium abundance of attached bacteria as a function of aggregate size, which is markedly different from field observations. This discrepancy suggests that inter- and intraspecific interactions among bacteria and between bacteria and their predators may be more important than colonization in governing the population dynamics of bacteria on natural aggregates.

  12. Bacterial colonization and extinction on marine aggregates: stochastic model of species presence and abundance

    PubMed Central

    Kramer, Andrew M; Lyons, M Maille; Dobbs, Fred C; Drake, John M

    2013-01-01

    Organic aggregates provide a favorable habitat for aquatic microbes, are efficiently filtered by shellfish, and may play a major role in the dynamics of aquatic pathogens. Quantifying this role requires understanding how pathogen abundance in the water and aggregate size interact to determine the presence and abundance of pathogen cells on individual aggregates. We build upon current understanding of the dynamics of bacteria and bacterial grazers on aggregates to develop a model for the dynamics of a bacterial pathogen species. The model accounts for the importance of stochasticity and the balance between colonization and extinction. Simulation results suggest that while colonization increases linearly with background density and aggregate size, extinction rates are expected to be nonlinear on small aggregates in a low background density of the pathogen. Under these conditions, we predict lower probabilities of pathogen presence and reduced abundance on aggregates compared with predictions based solely on colonization. These results suggest that the importance of aggregates to the dynamics of aquatic bacterial pathogens may be dependent on the interaction between aggregate size and background pathogen density, and that these interactions are strongly influenced by ecological interactions and pathogen traits. The model provides testable predictions and can be a useful tool for exploring how species-specific differences in pathogen traits may alter the effect of aggregates on disease transmission. PMID:24340173

  13. Nitrification potential and population dynamics of nitrifying bacterial biofilms in response to controlled shifts of ammonium concentrations in wastewater trickling filters.

    PubMed

    Almstrand, R; Lydmark, P; Sörensson, F; Hermansson, M

    2011-09-01

    Nitrogen removal in wastewater treatment is energy consuming and often carried out in biofilm nitrifying trickling filters (NTFs). We investigated nitrification potential and population dynamics of nitrifying bacteria in pilot-plant NTFs fed with full-scale plant wastewater with high (8-9 mg NH(4)(+)l(-1)) or low (<0.5mg NH(4)(+)l(-1)) ammonium concentrations. After ammonium shifts, nitrification potentials stabilized after 10-43 days depending on feed regime. An NTF fed with 3 days of high, and 4 days of low load per week reached a high nitrification potential, whereas a high load for 1 day a week gave a low potential. Nitrosomonas oligotropha dominated the AOB and changes in nitrification potentials were not explained by large population shifts to other AOBs. Although nitrification potentials were generally correlated with the relative amounts of AOB and NOB, this was not always the case. Ammonium feed strategies can be used to optimize wastewater treatment performance. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Frequency, size, and localization of bacterial aggregates on bean leaf surfaces.

    PubMed

    Monier, J-M; Lindow, S E

    2004-01-01

    Using epifluorescence microscopy and image analysis, we have quantitatively described the frequency, size, and spatial distribution of bacterial aggregates on leaf surfaces of greenhouse-grown bean plants inoculated with the plant-pathogenic bacterium Pseudomonas syringae pv. syringae strain B728a. Bacterial cells were not randomly distributed on the leaf surface but occurred in a wide range of cluster sizes, ranging from single cells to over 10(4) cells per aggregate. The average cluster size increased through time, and aggregates were more numerous and larger when plants were maintained under conditions of high relative humidity levels than under dry conditions. The large majority of aggregates observed were small (less than 100 cells), and aggregate sizes exhibited a strong right-hand-skewed frequency distribution. While large aggregates are not frequent on a given leaf, they often accounted for the majority of cells present. We observed that up to 50% of cells present on a leaf were located in aggregates containing 10(3) cells or more. Aggregates were associated with several different anatomical features of the leaf surface but not with stomates. Aggregates were preferentially associated with glandular trichomes and veins. The biological and ecological significance of aggregate formation by epiphytic bacteria is discussed.

  15. Formation mechanism of nitrifying granules observed in an aerobic upflow fluidized bed (AUFB) reactor.

    PubMed

    Tsuneda, S; Ejiri, Y; Nagano, T; Hirata, A

    2004-01-01

    The influences of trace metals in the wastewater and shear stress by aeration were particularly examined to clarify the formation mechanism of nitrifying granules in an aerobic upflow fluidized bed (AUFB) reactor. It was found that Fe added as a trace element to the inorganic wastewater accumulated at the central part of the nitrifying granules. Another result obtained was that suitable shear stress by moderate aeration (0.07-0.20 L/min/L-bed) promoted granulation. Furthermore, it was successfully demonstrated that pre-aggregation of seed sludge using hematite promoted core formation, leading to rapid production of nitrifying granules. From these results, a nitrifying granulation mechanism is proposed: 1) as a first step, nitrifying bacteria aggregate along with Fe precipitation, and then the cores of granules are formed; 2) as a second step, the aggregates grow to be spherical or elliptical in form due to multiplication of the nitrifying bacteria and moderate shear stress in the reactor, and then mature nitrifying granules are produced. Fluorescence in situ hybridization (FISH) analysis successfully visualized the change in the spatial distribution of nitrifying bacteria in the granules, which supports the proposed granulation mechanism.

  16. Using bacterial inclusion bodies to screen for amyloid aggregation inhibitors

    PubMed Central

    2012-01-01

    Background The amyloid-β peptide (Aβ42) is the main component of the inter-neuronal amyloid plaques characteristic of Alzheimer's disease (AD). The mechanism by which Aβ42 and other amyloid peptides assemble into insoluble neurotoxic deposits is still not completely understood and multiple factors have been reported to trigger their formation. In particular, the presence of endogenous metal ions has been linked to the pathogenesis of AD and other neurodegenerative disorders. Results Here we describe a rapid and high-throughput screening method to identify molecules able to modulate amyloid aggregation. The approach exploits the inclusion bodies (IBs) formed by Aβ42 when expressed in bacteria. We have shown previously that these aggregates retain amyloid structural and functional properties. In the present work, we demonstrate that their in vitro refolding is selectively sensitive to the presence of aggregation-promoting metal ions, allowing the detection of inhibitors of metal-promoted amyloid aggregation with potential therapeutic interest. Conclusions Because IBs can be produced at high levels and easily purified, the method overcomes one of the main limitations in screens to detect amyloid modulators: the use of expensive and usually highly insoluble synthetic peptides. PMID:22553999

  17. Influence of Calcium in Extracellular DNA Mediated Bacterial Aggregation and Biofilm Formation

    PubMed Central

    Koop, Leena; Wong, Yie Kuan; Ahmed, Safia; Siddiqui, Khawar Sohail; Manefield, Mike

    2014-01-01

    Calcium (Ca2+) has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA) being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca2+ and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynamics of DNA to Ca2+ binding. It was found that the eDNA concentrations under both planktonic and biofilm growth conditions were different among bacterial strains. Whilst Ca2+ had no influence on eDNA release, presence of eDNA by itself favours bacterial aggregation via attractive acid-base interactions in addition, its binding with Ca2+ at biologically relevant concentrations was shown further increase in bacterial aggregation via cationic bridging. Negative Gibbs free energy (ΔG) values in iTC data confirmed that the interaction between DNA and Ca2+ is thermodynamically favourable and that the binding process is spontaneous and exothermic owing to its highly negative enthalpy. Removal of eDNA through DNase I treatment revealed that Ca2+ alone did not enhance cell aggregation and biofilm formation. This discovery signifies the importance of eDNA and concludes that existence of eDNA on bacterial cell surfaces is a key facilitator in binding of Ca2+ to eDNA thereby mediating bacterial aggregation and biofilm formation. PMID:24651318

  18. Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

    PubMed

    Das, Theerthankar; Sehar, Shama; Koop, Leena; Wong, Yie Kuan; Ahmed, Safia; Siddiqui, Khawar Sohail; Manefield, Mike

    2014-01-01

    Calcium (Ca(2+)) has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA) being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca(2+) and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynamics of DNA to Ca(2+) binding. It was found that the eDNA concentrations under both planktonic and biofilm growth conditions were different among bacterial strains. Whilst Ca(2+) had no influence on eDNA release, presence of eDNA by itself favours bacterial aggregation via attractive acid-base interactions in addition, its binding with Ca(2+) at biologically relevant concentrations was shown further increase in bacterial aggregation via cationic bridging. Negative Gibbs free energy (ΔG) values in iTC data confirmed that the interaction between DNA and Ca(2+) is thermodynamically favourable and that the binding process is spontaneous and exothermic owing to its highly negative enthalpy. Removal of eDNA through DNase I treatment revealed that Ca(2+) alone did not enhance cell aggregation and biofilm formation. This discovery signifies the importance of eDNA and concludes that existence of eDNA on bacterial cell surfaces is a key facilitator in binding of Ca(2+) to eDNA thereby mediating bacterial aggregation and biofilm formation.

  19. A local PDE model of aggregation formation in bacterial colonies

    NASA Astrophysics Data System (ADS)

    Chavy-Waddy, Paul-Christopher; Kolokolnikov, Theodore

    2016-10-01

    We study pattern formation in a model of cyanobacteria motion recently proposed by Galante, Wisen, Bhaya and Levy. By taking a continuum limit of their model, we derive a novel fourth-order nonlinear parabolic PDE equation that governs the behaviour of the model. This PDE is {{u}t}=-{{u}xx}-{{u}xxxx}+α {{≤ft(\\frac{{{u}x}{{u}xx}}{u}\\right)}x} . We then derive the instability thresholds for the onset of pattern formation. We also compute analytically the spatial profiles of the steady state aggregation density. These profiles are shown to be of the form \\text{sec}{{\\text{h}}p} where the exponent p is related to the parameters of the model. Full numerical simulations give a favorable comparison between the continuum and the underlying discrete system, and show that the aggregation profiles are stable above the critical threshold.

  20. Oil-derived marine aggregates - hot spots of polysaccharide degradation by specialized bacterial communities

    NASA Astrophysics Data System (ADS)

    Arnosti, Carol; Ziervogel, Kai; Yang, Tingting; Teske, Andreas

    2016-07-01

    Aggregates generated in the laboratory from incubations of seawater and surface-water oil collected in the initial phase of the Deepwater Horizon oil spill resemble the oil-aggregates observed in situ. Here, we investigated the enzyme activities and microbial community composition of laboratory generated oil-aggregates, focusing on the abilities of these communities to degrade polysaccharides, which are major components of marine organic matter and are abundant constituents of exopolymeric substances (EPS) generated by oil-associated bacteria in response to the presence of oil. The patterns of polysaccharide-hydrolyzing enzyme activities in oil aggregates were very different from those in the water surrounding the aggregates after formation, and in the surface water that did not contain the oil. Specific oil aggregate-associated hydrolysis rates were also considerably higher than in the water surrounding the aggregates. The differences in initial hydrolysis profiles, and in evolution of these profiles with time, points to specialized metabolic abilities among the oil-aggregate communities compared to oil-water and ambient water communities. The composition of the oil-aggregate community indicates a multifunctional microbial assemblage containing primary oil-degrading and exopolysaccharide-producing members of the Gammaproteobacteria, and diverse members of the Alphaproteobacteria, Bacteroidetes and Planktomycetales that most likely participate in the breakdown of oil-derived bacterial biopolymers. Formation and aging of oil-aggregates encourages the growth and transformation of microbial communities that are specialized in degradation of petroleum, as well as their secondary degradation products.

  1. Co-composting of gelatin industry sludge combined with organic fraction of municipal solid waste and poultry waste employing zeolite mixed with enriched nitrifying bacterial consortium.

    PubMed

    Awasthi, Mukesh Kumar; Pandey, Akhilesh Kumar; Bundela, Pushpendra Singh; Wong, Jonathan W C; Li, Ronghua; Zhang, Zengqiang

    2016-08-01

    This work illustrates the co-composting of gelatin industry sludge (GIS) combined with organic fraction of municipal solid waste (OFMSW) and poultry waste (PW) employing 10% zeolite mixed with enriched nitrifying bacteria consortium (ENBC). Five piles of GIS were prepared mixed with OFMSW and PW at 2:1:0.5, 4:1:0.5, 6:1:0.5 and 8:1:0.5 and without GIS 0:1:0.5 (dry weight basis) served as control, while 10% zeolite mixed with ENBC was inoculated in all piles and composted for 42days. The Pile-4 with GIS, OFMSW and PW ratio 6:1:0.5 and 10% zeolite+ENBC were drastically reduced the nitrogen loss and enhance the mineralization rate as compare to other piles. The co-amendment of 6% GIS effectively buffered the pH between ∼7.5 to 8.0 and shortened the compost maturity period, while lower concentration of GIS was comparatively delayed the early decomposition. Therefore, our results suggested that suitability of 10% zeolite+ENBC with initial feedstock ratio 6:1:0.5 as the best formulation for the composting of GIS into value-added stable product.

  2. Recovery of soil ammonia oxidation after long-term zinc exposure is not related to the richness of the bacterial nitrifying community.

    PubMed

    Ruyters, Stefan; Springael, Dirk; Smolders, Erik

    2013-08-01

    A soil sterilization-reinoculation approach was used to manipulate soil microbial diversity and to assess the effect of the diversity of the ammonia-oxidizing bacteria (AOB) on the recovery of the nitrifying community to metal stress (zinc). Gamma-irradiated soil was inoculated with 13 different combinations of up to 22 different soils collected worldwide to create varying degrees of AOB diversity. Two months after inoculation, AOB amoA DGGE based diversity (weighted richness) varied more than 10-fold among the 13 treatments, the largest value observed where the number of inocula had been largest. Subsequently, the 13 treatments were either or not amended with ZnCl2. Initially, Zn amendment completely inhibited nitrification. After 6 months of Zn exposure, recovery of the potential nitrification activity in the Zn amended soils ranged from <10 % to >100 % of the potential nitrification activity in the corresponding non-amended soils. This recovery was neither related to DGGE-based indices of AOB diversity nor to the AOB abundance assessed 2 months after inoculation (p > 0.05). However, recovery was significantly related (r = 0.75) to the potential nitrification rate before Zn amendment and only weakly to the number of soil inocula used in the treatments (r = 0.46). The lack of clear effects of AOB diversity on recovery may be related to an inherently sufficient diversity and functional redundancy of AOB communities in soil. Our data indicate that potential microbial activity can be a significant factor in recovery.

  3. Pyrosequencing Analysis of Bench-Scale Nitrifying BiofiltersRemoving Trihalomethanes

    EPA Science Inventory

    The bacterial biofilm communities in four nitrifying biofilters degrading regulated drinking water trihalomethanes were characterized by 454 pyrosequencing. The three most abundant phylotypes based on total diversity were Nitrosomonas (70%), Nitrobacter (14%), and Chitinophagace...

  4. Pyrosequencing Analysis of Bench-Scale Nitrifying BiofiltersRemoving Trihalomethanes

    EPA Science Inventory

    The bacterial biofilm communities in four nitrifying biofilters degrading regulated drinking water trihalomethanes were characterized by 454 pyrosequencing. The three most abundant phylotypes based on total diversity were Nitrosomonas (70%), Nitrobacter (14%), and Chitinophagace...

  5. Bacterial density and community structure associated with aggregate size fractions of soil-feeding termite mounds.

    PubMed

    Fall, S; Nazaret, S; Chotte, J L; Brauman, A

    2004-08-01

    The building and foraging activities of termites are known to modify soil characteristics such as the heterogeneity. In tropical savannas the impact of the activity of soil-feeding termites ( Cubitermes niokoloensis) has been shown to affect the properties of the soil at the aggregate level by creating new soil microenvironments (aggregate size fractions) [13]. These changes were investigated in greater depth by looking at the microbial density (AODC) and the genetic structure (automated rRNA intergenic spacer analysis: ARISA) of the communities in the different aggregate size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, and dispersible clays) separated from compartments (internal and external wall) of three Cubitermes niokoloensis mounds. The bacterial density of the mounds was significantly higher (1.5 to 3 times) than that of the surrounding soil. Within the aggregate size fractions, the termite building activity resulted in a significant increase in bacterial density within the coarser fractions (>20 mum). Multivariate analysis of the ARISA profiles revealed that the bacterial genetic structures of unfractionated soil and soil aggregate size fractions of the three mounds was noticeably different from the savanna soil used as a reference. Moreover, the microbial community associated with the different microenvironments in the three termite mounds revealed three distinct clusters formed by the aggregate size fractions of each mound. Except for the 2-20 mum fraction, these results suggest that the mound microbial genetic structure is more dependent upon microbial pool affiliation (the termite mound) than on the soil location (aggregate size fraction). The causes of the specificity of the microbial community structure of termite mound aggregate size fractions are discussed.

  6. Visualizing tributyltin (TBT) in bacterial aggregates by specific rhodamine-based fluorescent probes.

    PubMed

    Jin, Xilang; Hao, Likai; She, Mengyao; Obst, Martin; Kappler, Andreas; Yin, Bing; Liu, Ping; Li, Jianli; Wang, Lanying; Shi, Zhen

    2015-01-01

    Here we present the first examples of fluorescent and colorimetric probes for microscopic TBT imaging. The fluorescent probes are highly selective and sensitive to TBT and have successfully been applied for imaging of TBT in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell-EPS-mineral aggregates and in cell suspensions of the marine cyanobacterium Synechococcus PCC 7002 by using confocal laser scanning microscopy.

  7. Postfragmentation density function for bacterial aggregates in laminar flow

    NASA Astrophysics Data System (ADS)

    Byrne, Erin; Bortz, David M.; Dzul, Steve; Solomon, Michael; Younger, John

    2011-04-01

    The postfragmentation probability density of daughter flocs is one of the least well-understood aspects of modeling flocculation. We use three-dimensional positional data of Klebsiella pneumoniae bacterial flocs in suspension and the knowledge of hydrodynamic properties of a laminar flow field to construct a probability density function of floc volumes after a fragmentation event. We provide computational results which predict that the primary fragmentation mechanism for large flocs is erosion. The postfragmentation probability density function has a strong dependence on the size of the original floc and indicates that most fragmentation events result in clumps of one to three bacteria eroding from the original floc. We also provide numerical evidence that exhaustive fragmentation yields a limiting density inconsistent with the log-normal density predicted in the literature, most likely due to the heterogeneous nature of K. pneumoniae flocs. To support our conclusions, artificial flocs were generated and display similar postfragmentation density and exhaustive fragmentation.

  8. Identification and Activities In Situ of Nitrosospira and Nitrospira spp. as Dominant Populations in a Nitrifying Fluidized Bed Reactor

    PubMed Central

    Schramm, Andreas; de Beer, Dirk; Wagner, Michael; Amann, Rudolf

    1998-01-01

    Bacterial aggregates from a chemolithoautotrophic, nitrifying fluidized bed reactor were investigated with microsensors and rRNA-based molecular techniques. The microprofiles of O2, NH4+, NO2−, and NO3− demonstrated the occurrence of complete nitrification in the outer 125 μm of the aggregates. The ammonia oxidizers were identified as members of the Nitrosospira group by fluorescence in situ hybridization (FISH). No ammonia- or nitrite-oxidizing bacteria of the genus Nitrosomonas or Nitrobacter, respectively, could be detected by FISH. To identify the nitrite oxidizers, a 16S ribosomal DNA clone library was constructed and screened by denaturing gradient gel electrophoresis and selected clones were sequenced. The organisms represented by these sequences formed two phylogenetically distinct clusters affiliated with the nitrite oxidizer Nitrospira moscoviensis. 16S rRNA-targeted oligonucleotide probes were designed for in situ detection of these organisms. FISH analysis showed that the dominant populations of Nitrospira spp. and Nitrosospira spp. formed separate, dense clusters which were in contact with each other and occurred throughout the aggregate. A second, smaller, morphologically and genetically different population of Nitrospira spp. was restricted to the outer nitrifying zones. PMID:9726900

  9. Spatial organization of dual-species bacterial aggregates on leaf surfaces.

    PubMed

    Monier, J-M; Lindow, S E

    2005-09-01

    The spatial organization of cells within bacterial aggregates on leaf surfaces was determined for pair-wise mixtures of three different bacterial species commonly found on leaves, Pseudomonas syringae, Pantoea agglomerans, and Pseudomonas fluorescens. Cells were coinoculated onto bean plants and allowed to grow under moist conditions, and the resulting aggregates were examined in situ by epifluorescence microscopy. Each bacterial strain could be localized because it expressed either the green or the cyan fluorescent protein constitutively, and the viability of individual cells was assessed by propidium iodide staining. Each pair of bacterial strains that was coinoculated onto leaves formed mixed aggregates. The degree of segregation of cells in mixed aggregates differed between the different coinoculated pairs of strains and was higher in mixtures of P. fluorescens A506 and P. agglomerans 299R and mixtures of P. syringae B728a and P. agglomerans 299R than in mixtures of two isogenic strains of P. agglomerans 299R. The fractions of the total cell population that were dead in mixed and monospecific aggregates of a gfp-marked strain of P. agglomerans 299R and a cfp-marked strain of P. agglomerans 299R, or of P. fluorescens A506 and P. agglomerans 299R, were similar. However, the proportion of dead cells in mixed aggregates of P. syringae B728a and P. agglomerans 299R was significantly higher (13.2% +/- 8.2%) than that in monospecific aggregates of these two strains (1.6% +/- 0.7%), and it increased over time. While dead cells in such mixed aggregates were preferentially found at the interface between clusters of cells of these strains, cells of these two strains located at the interface did not exhibit equal probabilities of mortality. After 9 days of incubation, about 77% of the P. agglomerans 299R cells located at the interface were dead, while only about 24% of the P. syringae B728a cells were dead. The relevance of our results to understanding bacterial

  10. Structure and community composition of sprout-like bacterial aggregates in a Dinaric Karst subterranean stream.

    PubMed

    Kostanjšek, Rok; Pašić, Lejla; Daims, Holger; Sket, Boris

    2013-07-01

    The Vjetrenica cave in the Dinaric Karst hosts a worldwide extraordinarily high cave biodiversity. Beside a diverse and specialized cave fauna, sprout-like formations attached to the bed of the cave stream were observed and described, but not further characterized, almost a century ago. Here we investigated these sprout-like microbial aggregates by the rRNA approach and detailed microscopy. Based on fluorescence in situ hybridization and ultrastructural analysis, the sprout-like formations are morphologically highly organized, and their core consists of a member of a novel deep-branching lineage in the bacterial phylum Nitrospirae. This organism displays an interesting cellular ultrastructure with different kinds of cytoplasmic inclusions and is embedded in a thick extracellular matrix, which contributes to the stability and shape of the aggregates. This novel bacterium has been provisionally classified as "Candidatus Troglogloea absoloni." The surface of the sprout-like aggregates is more diverse than the core. It is colonized by a bacterial biofilm consisting primarily of filamentous Betaproteobacteria, whereas other microbial populations present in the crust include members of the Bacteriodetes, Gammaproteobacteria, Actinombacteria, Alphaproteobacteria, and Planctomycetes, which are intermingled with mineral inclusions. This study represents the first thorough molecular and ultrastructural characterization of the elusive sprout-like bacterial aggregates, which are also found in other cave systems of the Dinaric Karst. The discovery of Ca. Troglogloea absoloni contributes to the known biodiversity of subterranean ecosystems and especially of macroscopic structures formed in caves by microorganisms, whose composition and ecological function often remain enigmatic.

  11. Bacterial aggregates in the tentacles of the sea anemone Metridium senile

    NASA Astrophysics Data System (ADS)

    Schuett, Christian; Doepke, Hilke; Grathoff, Annette; Gedde, Michael

    2007-09-01

    This paper provides first information on organ-like bacterial aggregates in the tentacles of the sea anemone Metridium senile. The specimens were collected from waters near Helgoland (German Bight, North Sea) and the Orkney Islands. Tentacles were prepared for morphological inspection by light and scanning electron microscopy as well as for the phylogenetic analysis of endocytic bacteria. Bacterial aggregates are located in caverns of the tentacles’ epidermis. The aggregates are enwrapped in thin envelopes, which contain coccoid and/or rod-shaped tightly packed bacteria of different division states. Most of the bacterial cells are connected by fine filamentous structures. The phylogenetic determination is based on the sequence data of the 16S rDNA derived from tentacle material. Sequence analysis revealed three different subgroups of intratentacular proteobacteria. The dominant band, detected in all of the samples tested, showed a close relationship (98%) to a gram-negative Endozoicimonas elysicola. Two bands, only detected in tentacles of M. senile from Helgoland were assigned to Pseudomonas saccherophilia (99%), a knallgas bacterium, and to Ralstonia pickettii (100%). The bacteria represent a specific bacterial community. Their DGGE profiles do not correspond to the profiles of the planktonic bacteria generated from seawater close to the habitats of the anemones. The allocation of DNA sequences to the different morphotypes, their isolation, culturing and the elucidation of the physiological functions of intratentacular bacteria are in progress.

  12. Bacterial exopolysaccharide and biofilm formation stimulate chickpea growth and soil aggregation under salt stress

    PubMed Central

    Qurashi, Aisha Waheed; Sabri, Anjum Nasim

    2012-01-01

    To compensate for stress imposed by salinity, biofilm formation and exopolysaccharide production are significant strategies of salt tolerant bacteria to assist metabolism. We hypothesized that two previously isolated salt-tolerant strains Halomonas variabilis (HT1) and Planococcus rifietoensis (RT4) have an ability to improve plant growth, These strains can form biofilm and accumulate exopolysacharides at increasing salt stress. These results showed that bacteria might be involved in developing microbial communities under salt stress and helpful in colonizing of bacterial strains to plant roots and soil particles. Eventually, it can add to the plant growth and soil structure. We investigated the comparative effect of exopolysacharide and biofilm formation in two bacterial strains Halomonas variabilis (HT1) and Planococcus rifietoensis (RT4) in response to varying salt stress. We found that biofilm formation and exopolysaccharide accumulation increased at higher salinity. To check the effect of bacterial inoculation on the plant (Cicer arietinum Var. CM-98) growth and soil aggregation, pot experiment was conducted by growing seedlings under salt stress. Inoculation of both strains increased plant growth at elevated salt stress. Weight of soil aggregates attached with roots and present in soil were added at higher salt concentrations compared to untreated controls. Soil aggregation was higher at plant roots under salinity. These results suggest the feasibility of using above strains in improving plant growth and soil fertility under salinity. PMID:24031943

  13. Community Composition and Abundance of Bacterial, Archaeal and Nitrifying Populations in Savanna Soils on Contrasting Bedrock Material in Kruger National Park, South Africa

    PubMed Central

    Rughöft, Saskia; Herrmann, Martina; Lazar, Cassandre S.; Cesarz, Simone; Levick, Shaun R.; Trumbore, Susan E.; Küsel, Kirsten

    2016-01-01

    Savannas cover at least 13% of the global terrestrial surface and are often nutrient limited, especially by nitrogen. To gain a better understanding of their microbial diversity and the microbial nitrogen cycling in savanna soils, soil samples were collected along a granitic and a basaltic catena in Kruger National Park (South Africa) to characterize their bacterial and archaeal composition and the genetic potential for nitrification. Although the basaltic soils were on average 5 times more nutrient rich than the granitic soils, all investigated savanna soil samples showed typically low nutrient availabilities, i.e., up to 38 times lower soil N or C contents than temperate grasslands. Illumina MiSeq amplicon sequencing revealed a unique soil bacterial community dominated by Actinobacteria (20–66%), Chloroflexi (9–29%), and Firmicutes (7–42%) and an increase in the relative abundance of Actinobacteria with increasing soil nutrient content. The archaeal community reached up to 14% of the total soil microbial community and was dominated by the thaumarchaeal Soil Crenarchaeotic Group (43–99.8%), with a high fraction of sequences related to the ammonia-oxidizing genus Nitrosopshaera sp. Quantitative PCR targeting amoA genes encoding the alpha subunit of ammonia monooxygenase also revealed a high genetic potential for ammonia oxidation dominated by archaea (~5 × 107 archaeal amoA gene copies g−1 soil vs. mostly < 7 × 104 bacterial amoA gene copies g−1 soil). Abundances of archaeal 16S rRNA and amoA genes were positively correlated with soil nitrate, N and C contents. Nitrospira sp. was detected as the most abundant group of nitrite oxidizing bacteria. The specific geochemical conditions and particle transport dynamics at the granitic catena were found to affect soil microbial communities through clay and nutrient relocation along the hill slope, causing a shift to different, less diverse bacterial and archaeal communities at the footslope. Overall, our

  14. Association of running manner with bacterial community dynamics in a partial short-term nitrifying bioreactor for treatment of piggery wastewater with high ammonia content.

    PubMed

    Du, Wei-Li; Huang, Qiang; Miao, Li-Li; Liu, Ying; Liu, Zhi-Pei

    2016-12-01

    Optimization of running parameters in a bioreactor requires detailed understanding of microbial community dynamics during the startup and running periods. Using a novel piggery wastewater treatment system termed "UASB + SHARON + ANAMMOX" constructed in our laboratory, we investigated microbial community dynamics using the Illumina MiSeq method, taking activated sludge samples at ~2-week intervals during a ~300-day period. Ammonia-oxidizing bacteria (AOB) were further investigated by quantification of AOB amoA genes and construction of gene clone libraries. Major changes in bacterial community composition and dynamics occurred when running manner was changed from continuous flow manner (CFM) to sequencing batch manner (SBM), and when effluent from an upflow anaerobic sludge blanket (UASB) reactor for practical treatment of real piggery wastewater was used as influent; differences among these three experimental groups were significant (R (2)  = 0.94, p < 0.01). When running manner was changed from CFM to SBM, relative abundance of the genus Nitrospira decreased sharply from 18.1 % on day 116 to 1.5 % on day 130, and to undetectable level thereafter. Relative abundance of the genus Nitrosomonas increased from ~0.67 % during the CFM period to 8.0 % by day 220, and thereafter decreased to a near-constant ~1.6 %. Environmental factors such as load ammonia, effluent ammonia, effluent nitrite, UASB effluent, pH, and DO levels collectively drove bacterial community dynamics and contributed to maintenance of effluent NH4 (+)-N/NO2 (-)-N ratio ~1. Theses results might provide useful clues for the control of the startup processes and maintaining high efficiency of such bioreactors.

  15. Extracellular enzyme activity and dynamics of bacterial community in mucilaginous aggregates of the northern Adriatic Sea.

    PubMed

    Zoppini, Annamaria; Puddu, Alberto; Fazi, Stefano; Rosati, Michela; Sist, Paola

    2005-12-15

    Bacterial degradation of mucilaginous aggregates (creamy layers, stringers and macroflocs) collected during two summer events (2001-2002) was tested. The objective was to describe the temporal trend of the bacterial activity, abundance and composition in the aggregated and dissolved organic matter under different trophic conditions. In the native aggregates proteins and organic phosphorous were actively hydrolyzed as aminopeptidase and alkaline phosphatase activities represented up to 87% and 25% of total activity, respectively; polysaccharides were less hydrolyzed and the highest activities were observed for beta-glucosidase (5% of the total). This hydrolysation pattern tends to a progressive accumulation of long persistent polysaccharides. During short term incubations nutrient addition (P, N and Glucose) differently stimulated bacterial growth in the seawater: P played the main role in stimulating bacterial production from 3 to 6 folds higher than in the control, whereas a secondary C-limitation was observed only for bacteria growing on seawater from macroflocs. This scarce dissolved organic carbon (DOC) bioavailability was confirmed by the lower DOC removal (13% macroflocs, 36% stringers). The total amount of carbon incorporated by bacteria living on aggregates was similar (0.58 mg C L(-1)) both in the control and under P enrichments showing a more balanced condition with respect to the seawater. Hence the well-known P limitation in the Northern Adriatic Sea affects only dissolved organic carbon uptake without influencing the uptake of aggregated organic matter. Organic matter limitation was observed only on stringers--total C incorporated raised to 0.96 mg C L(-1) after PNG addition. Macroflocs release of refractory compounds leads to DOC accumulation (73 microM DOC) contributing to inflate the pool of refractory DOC in the surrounding waters. Several evidences, including different monosaccharide composition of stringers and macroflocs (glucose 15% and 56% on

  16. Glyphosate applications,glyphosate resistant corn, and tillage on nitrification rates and distribution of nitrifying microbial communities

    USDA-ARS?s Scientific Manuscript database

    Conservation tillage practices have combined genetically modified glyphosate resistant corn crops along with applications of the herbicide glyphosate. We tested the null hypothesis that the soil process of nitrification and the distribution of archaeal and bacterial nitrifying communities would not ...

  17. Dynamics of the diversity and structure of the overall and nitrifying microbial community in activated sludge along gradient copper exposures.

    PubMed

    Ouyang, Fan; Ji, Min; Zhai, Hongyan; Dong, Zhao; Ye, Lin

    2016-08-01

    Diversity and composition of the microbial community, especially the nitrifiers, are essential to the treatment efficiency of wastewater in activated sludge systems. Heavy metals commonly present in the wastewater influent such as Cu can alter the community structure of nitrifiers and lower their activity. However, the dynamics of microbial community along a gradient of metal exposure have largely been unexplored, partially due to the limitations in traditional molecular methods. This study explored the dynamics regarding the diversity and community structures of overall and nitrifying microbial communities in activated sludge under intermittent Cu gradient loadings using Illumina sequencing. We created a new local nitrifying bacterial database for sequence BLAST searches. High Cu loadings (>10.9 mg/L) impoverished microbial diversity and altered the microbial community. Overall, Proteobacteria was the predominant phylum in the activated sludge system, in which Zoogloea, Thauera, and Dechloromonas (genera within the Rhodocyclaceae family of the Beta-proteobacteria class) were the dominant genera in the presence of Cu. The abundance of unclassified bacteria at the phylum level increased substantially with increasing Cu loadings. Nitrosomonas and Nitrospira were the predominant nitrifiers. The nitrifying bacterial community changed through increasing abundance and shifting to Cu-tolerant species to reduce the toxic effects of Cu. Our local nitrifying bacterial database helped to improve the resolution of bacterial identification. Our results provide insights into the dynamics of microbial community in response to various metal concentrations in activated sludge systems and improve our understanding regarding the effect of metals on wastewater treatment efficiency.

  18. Multiscale modeling of bacterial colonies: how pili mediate the dynamics of single cells and cellular aggregates

    NASA Astrophysics Data System (ADS)

    Pönisch, Wolfram; Weber, Christoph A.; Juckeland, Guido; Biais, Nicolas; Zaburdaev, Vasily

    2017-01-01

    Neisseria gonorrhoeae is the causative agent of one of the most common sexually transmitted diseases, gonorrhea. Over the past two decades there has been an alarming increase of reported gonorrhea cases where the bacteria were resistant to the most commonly used antibiotics thus prompting for alternative antimicrobial treatment strategies. The crucial step in this and many other bacterial infections is the formation of microcolonies, agglomerates consisting of up to several thousands of cells. The attachment and motility of cells on solid substrates as well as the cell-cell interactions are primarily mediated by type IV pili, long polymeric filaments protruding from the surface of cells. While the crucial role of pili in the assembly of microcolonies has been well recognized, the exact mechanisms of how they govern the formation and dynamics of microcolonies are still poorly understood. Here, we present a computational model of individual cells with explicit pili dynamics, force generation and pili-pili interactions. We employ the model to study a wide range of biological processes, such as the motility of individual cells on a surface, the heterogeneous cell motility within the large cell aggregates, and the merging dynamics and the self-assembly of microcolonies. The results of numerical simulations highlight the central role of pili generated forces in the formation of bacterial colonies and are in agreement with the available experimental observations. The model can quantify the behavior of multicellular bacterial colonies on biologically relevant temporal and spatial scales and can be easily adjusted to include the geometry and pili characteristics of various bacterial species. Ultimately, the combination of the microbiological experimental approach with the in silico model of bacterial colonies might provide new qualitative and quantitative insights on the development of bacterial infections and thus pave the way to new antimicrobial treatments.

  19. Measurement Errors in Microbial Water Quality Assessement: the Case of Bacterial Aggregates

    NASA Astrophysics Data System (ADS)

    Plancherel, Y.; Cowen, J. P.

    2004-12-01

    The quantification of the risk of illness for swimmers, bathers, or consumers exposed to a polluted water body involves the measurement of microbial indicator organism densities. Depending on the organism targeted, there exist two widely used (traditional) techniques for their enumeration: most probable number (MPN) and membrane filtration (MF). Estimation of indicator organism density by these traditional methods is subject to large measurement error, which translates into poorly constrained relationships between indicator organism density and illness rate. Neither the MPN nor the MF method can discriminate multiple cells that form an aggregate. Mathematical formulations and computer simulations are used to investigate the effects that bacterial clumps have on the measurement error of the concentrations. The first case considered is that of the formation of clusters induced during the membrane filtration process assuming a randomly distributed population of cells growing into colonies. The computer simulations indicate that this process induces a typical measurement error <15% with the MF method. Replication of the MF measurements does not reduce this type of error. The second case describes a mathematical framework for the modeling of particle-associated bacteria. When aggregates harboring bacteria are present in a sample, an additional measurement error of 5-35% is expected. Empirical results from laboratory and field experiments enumerating aggregated bacteria using the MF method agree well with these model values. Furthermore, the data reveal that this type of error depends on the microbial indicators used (Enterococcus, C. perfringens, Heterotrophic Plate Count bacteria) and highlights the importance of small bacterial clusters (<5 μ m).

  20. ARK: Aggregation of Reads by K-Means for Estimation of Bacterial Community Composition.

    PubMed

    Koslicki, David; Chatterjee, Saikat; Shahrivar, Damon; Walker, Alan W; Francis, Suzanna C; Fraser, Louise J; Vehkaperä, Mikko; Lan, Yueheng; Corander, Jukka

    2015-01-01

    Estimation of bacterial community composition from high-throughput sequenced 16S rRNA gene amplicons is a key task in microbial ecology. Since the sequence data from each sample typically consist of a large number of reads and are adversely impacted by different levels of biological and technical noise, accurate analysis of such large datasets is challenging. There has been a recent surge of interest in using compressed sensing inspired and convex-optimization based methods to solve the estimation problem for bacterial community composition. These methods typically rely on summarizing the sequence data by frequencies of low-order k-mers and matching this information statistically with a taxonomically structured database. Here we show that the accuracy of the resulting community composition estimates can be substantially improved by aggregating the reads from a sample with an unsupervised machine learning approach prior to the estimation phase. The aggregation of reads is a pre-processing approach where we use a standard K-means clustering algorithm that partitions a large set of reads into subsets with reasonable computational cost to provide several vectors of first order statistics instead of only single statistical summarization in terms of k-mer frequencies. The output of the clustering is then processed further to obtain the final estimate for each sample. The resulting method is called Aggregation of Reads by K-means (ARK), and it is based on a statistical argument via mixture density formulation. ARK is found to improve the fidelity and robustness of several recently introduced methods, with only a modest increase in computational complexity. An open source, platform-independent implementation of the method in the Julia programming language is freely available at https://github.com/dkoslicki/ARK. A Matlab implementation is available at http://www.ee.kth.se/ctsoftware.

  1. Transient aggregation and long-time diffusion of bacterial suspensions in time periodic flows

    NASA Astrophysics Data System (ADS)

    Qin, Boyang; Winter, Rebecca; Gurjar, Madhura; Gagnon, David; Patteson, Alison; Arratia, Paulo

    2016-11-01

    In this talk, the transport dynamics of swimming bacteria in time-periodic flows is investigated in experiments and simulations. Experiments are performed by introducing swimming bacteria (Vibrio cholerae) in a low Reynolds number, two-dimensional flow driven electromagnetically. We observe two distinct transport regimes: (i) entrapment of bacteria inside vortex and near elliptic points and (ii) aggregation and subsequent transport along the flow manifolds. These time-dependent behaviors are set by the interaction between swimmer kinematics (e.g. speed, tumbling frequency, etc) and flow properties. Numerical simulation using a stochastic Langevin model are able to capture the main experimental results including the entrapment of bacteria near elliptic points and the rapid spreading along manifolds. Results show a significant reduction in long-time effective diffusion of the swimmer as vortex strength is increased. The conditions for bacterial entrapment in vortex flows are discussed.

  2. The effects of nutrient chemotaxis on bacterial aggregation patterns with non-linear degenerate cross diffusion

    NASA Astrophysics Data System (ADS)

    Leyva, J. Francisco; Málaga, Carlos; Plaza, Ramón G.

    2013-11-01

    This paper studies a reaction-diffusion-chemotaxis model for bacterial aggregation patterns on the surface of thin agar plates. It is based on the non-linear degenerate cross diffusion model proposed by Kawasaki et al. (1997) [5] and it includes a suitable nutrient chemotactic term compatible with such type of diffusion, as suggested by Ben-Jacob et al. (2000) [20]. An asymptotic estimation predicts the growth velocity of the colony envelope as a function of both the nutrient concentration and the chemotactic sensitivity. It is shown that the growth velocity is an increasing function of the chemotactic sensitivity. High resolution numerical simulations using Graphic Processing Units (GPUs), which include noise in the diffusion coefficient for the bacteria, are presented. The numerical results verify that the chemotactic term enhances the velocity of propagation of the colony envelope. In addition, the chemotaxis seems to stabilize the formation of branches in the soft-agar, low-nutrient regime.

  3. Mucin biopolymers prevent bacterial aggregation by retaining cells in the free-swimming state

    PubMed Central

    Caldara, Marina; Friedlander, Ronn S.; Kavanaugh, Nicole L.; Aizenberg, Joanna; Foster, Kevin R.; Ribbeck, Katharina

    2013-01-01

    Summary Many species of bacteria form surface-attached communities known as biofilms. Surrounded in secreted polymers, these aggregates are difficult to both prevent and eradicate, posing problems for medicine and industry [1, 2]. Humans play host to hundreds of trillions of microbes that live adjacent to our epithelia and we are typically able to prevent harmful colonization. Mucus, the hydrogel overlying all wet epithelia in the body, can prevent bacterial contact with the underlying tissue. The digestive tract, for example, is lined by a firmly adherent mucus layer that is typically devoid of bacteria, followed by a second, loosely adherent layer that contains numerous bacteria [3]. Here, we investigate mucus's role as a principle arena for host-microbe interactions. Using defined in vitro assays, we found that mucin biopolymers, the main functional constituents of mucus, promote the motility of planktonic bacteria, and prevent their adhesion to underlying surfaces. The deletion of motility genes, however, allows Pseudomonas aeruginosa to overcome the dispersive effects of mucus and form suspended antibiotic-resistant flocs, which mirror the clustered morphology of immotile natural isolates found in the cystic fibrosis lung mucus [4, 5]. Mucus may offer new strategies to target bacterial virulence, such as the design of anti-biofilm coatings for implants. PMID:23142047

  4. Mucin biopolymers prevent bacterial aggregation by retaining cells in the free-swimming state.

    PubMed

    Caldara, Marina; Friedlander, Ronn S; Kavanaugh, Nicole L; Aizenberg, Joanna; Foster, Kevin R; Ribbeck, Katharina

    2012-12-18

    Many species of bacteria form surface-attached communities known as biofilms. Surrounded in secreted polymers, these aggregates are difficult both to prevent and eradicate, posing problems for medicine and industry. Humans play host to hundreds of trillions of microbes that live adjacent to our epithelia, and we are typically able to prevent harmful colonization. Mucus, the hydrogel overlying all wet epithelia in the body, can prevent bacterial contact with the underlying tissue. The digestive tract, for example, is lined by a firmly adherent mucus layer that is typically devoid of bacteria, followed by a second, loosely adherent layer that contains numerous bacteria. Here, we investigate the role of mucus as a principle arena for host-microbe interactions. Using defined in vitro assays, we found that mucin biopolymers, the main functional constituents of mucus, promote the motility of planktonic bacteria and prevent their adhesion to underlying surfaces. The deletion of motility genes, however, allows Pseudomonas aeruginosa to overcome the dispersive effects of mucus and form suspended antibiotic-resistant flocs, which mirror the clustered morphology of immotile natural isolates found in the cystic fibrosis lung mucus. Mucus may offer new strategies to target bacterial virulence, such as the design of antibiofilm coatings for implants. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Using mineral trioxide aggregate powder as an apical barrier: a bacterial leakage study.

    PubMed

    Milani, Amin Salem; Jafarabadi, Mohammad Asghari; Pakdel, Mahdi Vahid

    2014-01-01

    Mineral trioxide aggregate (MTA) has been used successfully for the treatment of necrotic immature teeth as part of a 2-step apical barrier. Recently, some researchers have used MTA powder instead of wet-mix MTA. It has also been used in a single-step approach in order to decrease the number of patient appointments. The aim of this study was to evaluate the bacterial microleakage of MTA powder in comparison with wet-mix MTA, in single or 2-step barrier approaches. This ex vivo study was carried out on 70 extracted single-rooted teeth. The canals were enlarged to simulate immature teeth. The prepared specimens were assigned to 4 experimental (n = 15) and 2 control (n = 5) groups. In Group 1, a wet paper point was placed in the canal following placement of wet-mix MTA. In Group 2, a dry paper point was placed on wet-mix MTA. In Group 3, the samples were treated similar to Group 1, but MTA powder was used instead of wet-mix MTA. In Group 4, the same procedures were followed as Group 3 except that a dry paper point was used. Microleakage of the samples was compared using a 2-chamber bacterial leakage apparatus. Results showed that there were no significant differences in the number of leaked samples or rate of leakage over time (P > 0.05) among the experimental groups. It can be concluded that MTA used in a single step approach has the same resistance against bacterial penetration as in a 2-step approach, and MTA powder provides the same sealing ability as wet-mix MTA.

  6. Bacterial diversity of soil aggregates of different sizes in various land use conditions

    NASA Astrophysics Data System (ADS)

    Ivanova, Ekaterina; Azida, Thakahova; Olga, Kutovaya

    2014-05-01

    The patterns of soil microbiome structure may be a universal and very sensitive indicator of soil quality (soil "health") used for optimization and biologization of agricultural systems. The understanding of how microbial diversity influenses, and is influenced by, the environment can only be attained by analyses at scales relevant to those at which processes influencing microbial diversity actually operate. The basic structural and functional unit of the soil is a soil aggregate, which is actually a microcosm of the associative co-existing groups of microorganisms that form characteristic ecological food chains. It is known that many important microbial processes occur in spatially segregated microenvironments in soil leading to a microscale biogeography. The Metagenomic library of typical chernozem in conditions of different land use systems was created. Total genomic DNA was extracted from 0.5 g of the frozen soil after mechanical destruction. Sample preparation and sequencing was performed on a GS Junior ("Roche»", Switzerland) according to manufacturer's recommendations, using the universal primers to the variable regions V4 gene 16S - rRNA - F515 (GTGCCAGCMGCCGCGGTAA) and R806 (GGACT-ACVSGGGTATCTAAT). It is shown that the system of land use is a stronger determinant of the taxonomic composition of the soil microbial community, rather than the size of the structural units. In soil samples from different land use systems the presence of accessory components was revealed. They may be used as indicators of processes of soil recovery, soil degradation or soil exhaustion processes occuring in the agroecosystems. The comparative analysis of microbial communities of chernozem aggregates investigated demonstrates the statistically valuable differences in the amount of bacterial phyla and Archean domain content as well as the species richness in aggregates of various size fractions. The occurrence of specific components in the taxonomic structure of micro-and macro-aggregates

  7. Pyrosequencing and mid-infrared spectroscopy techniques reveal distinct aggregate stratification of soil bacterial communities and organic matter composition

    USDA-ARS?s Scientific Manuscript database

    This study integrated physical, chemical, and molecular techniques to assess relationships between soil bacterial community structures and the quantity and quality of soil organic carbon (SOC) at the soil microenvironment scale (e.g., within different aggregate size-fractions). To accomplish this g...

  8. Aggregate stratification assessment of soil bacterial communities and organic matter composition: Coupling pyrosequencing and mid-infrared spectroscopy techniques

    USDA-ARS?s Scientific Manuscript database

    This study integrated physical, chemical, and molecular techniques to assess relationships between soil bacterial communities and the quantity and quality of soil organic carbon (SOC) at the soil microenvironment scale (e.g., within different aggregate size-fractions). To accomplish this goal soil ...

  9. Enhancement of platelet response to immune complexes and IgG aggregates by lipid A-rich bacterial lipopolysaccharides

    PubMed Central

    1978-01-01

    The effect of the common lipid moiety of bacterial LPS on secretion from washed human platelets has been studied. The lipid A-rich LPS of S. minnesota R595 and a lipid A preparation both potentiated platelet serotonin secretion in response to IgG aggregates or immune complexes up to 50-fold but had little effect in the absence of IgG. Lipid A has been shown to bind immune aggregates, raising the possibility that its mechanism of action involved effective enlargement or insolubilization of the aggregates. IgG aggregates of dimer to tetramer size were shown to be platelet simuli, equivalent on a weight basis to larger soluble aggregates. The effect of both sizes of aggregates on platelets were equally enhanced by the LPS, indicating that increased size of aggregates alone could not account for the effect of LPS. Similarly, because lipid A-rich LPS enhanced platelet response to already insoluble immune complexes, its mechanism of action cannot simply be insolubilization of immune aggregates. These LPS did not enhance platelet stimulation by antiplatelet antibody, monosodium urate crystals, or thrombin and only slightly enhanced stimulation by insoluble human skin collagen. This indicates some stimulus specificity in the ability of LPS to increase platelet secretion. The enhancement of cell response to immune complexes by the common lipid region of LPS may represent a mechanism for the diverse effects of LPS in vivo and in vitro. PMID:627836

  10. Novel bacterial isolate from Permian groundwater, capable of aggregating potential biofuel-producing microalga Nannochloropsis oceanica IMET1.

    PubMed

    Wang, Hui; Laughinghouse, Haywood D; Anderson, Matthew A; Chen, Feng; Willliams, Ernest; Place, Allen R; Zmora, Odi; Zohar, Yonathan; Zheng, Tianling; Hill, Russell T

    2012-03-01

    Increasing petroleum costs and climate change have resulted in microalgae receiving attention as potential biofuel producers. Little information is available on the diversity and functions of bacterial communities associated with biofuel-producing algae. A potential biofuel-producing microalgal strain, Nannochloropsis oceanica IMET1, was grown in Permian groundwater. Changes in the bacterial community structure at three temperatures were monitored by two culture-independent methods, and culturable bacteria were characterized. After 9 days of incubation, N. oceanica IMET1 began to aggregate and precipitate in cultures grown at 30°C, whereas cells remained uniformly distributed at 15°C and 25°C. The bacterial communities in cultures at 30°C changed markedly. Some bacteria isolated only at 30°C were tested for their potential for aggregating microalgae. A novel bacterium designated HW001 showed a remarkable ability to aggregate N. oceanica IMET1, causing microalgal cells to aggregate after 3 days of incubation, while the total lipid content of the microalgal cells was not affected. Direct interaction of HW001 and N. oceanica is necessary for aggregation. HW001 can also aggregate the microalgae N. oceanica CT-1, Tetraselmis suecica, and T. chuii as well as the cyanobacterium Synechococcus WH8007. 16S rRNA gene sequence comparisons indicated the great novelty of this strain, which exhibited only 89% sequence similarity with any previously cultured bacteria. Specific primers targeted to HW001 revealed that the strain originated from the Permian groundwater. This study of the bacterial communities associated with potential biofuel-producing microalgae addresses a little-investigated area of microalgal biofuel research and provides a novel approach to harvest biofuel-producing microalgae by using the novel bacterium strain HW001.

  11. Novel Bacterial Isolate from Permian Groundwater, Capable of Aggregating Potential Biofuel-Producing Microalga Nannochloropsis oceanica IMET1

    PubMed Central

    Wang, Hui; Laughinghouse, Haywood D.; Anderson, Matthew A.; Chen, Feng; Willliams, Ernest; Place, Allen R.; Zmora, Odi; Zohar, Yonathan

    2012-01-01

    Increasing petroleum costs and climate change have resulted in microalgae receiving attention as potential biofuel producers. Little information is available on the diversity and functions of bacterial communities associated with biofuel-producing algae. A potential biofuel-producing microalgal strain, Nannochloropsis oceanica IMET1, was grown in Permian groundwater. Changes in the bacterial community structure at three temperatures were monitored by two culture-independent methods, and culturable bacteria were characterized. After 9 days of incubation, N. oceanica IMET1 began to aggregate and precipitate in cultures grown at 30°C, whereas cells remained uniformly distributed at 15°C and 25°C. The bacterial communities in cultures at 30°C changed markedly. Some bacteria isolated only at 30°C were tested for their potential for aggregating microalgae. A novel bacterium designated HW001 showed a remarkable ability to aggregate N. oceanica IMET1, causing microalgal cells to aggregate after 3 days of incubation, while the total lipid content of the microalgal cells was not affected. Direct interaction of HW001 and N. oceanica is necessary for aggregation. HW001 can also aggregate the microalgae N. oceanica CT-1, Tetraselmis suecica, and T. chuii as well as the cyanobacterium Synechococcus WH8007. 16S rRNA gene sequence comparisons indicated the great novelty of this strain, which exhibited only 89% sequence similarity with any previously cultured bacteria. Specific primers targeted to HW001 revealed that the strain originated from the Permian groundwater. This study of the bacterial communities associated with potential biofuel-producing microalgae addresses a little-investigated area of microalgal biofuel research and provides a novel approach to harvest biofuel-producing microalgae by using the novel bacterium strain HW001. PMID:22194289

  12. Bacterial and yeast chaperones reduce both aggregate formation and cell death in mammalian cell models of Huntington's disease

    PubMed Central

    Carmichael, Jenny; Chatellier, Jean; Woolfson, Adrian; Milstein, César; Fersht, Alan R.; Rubinsztein, David C.

    2000-01-01

    Huntington's disease (HD) is an autosomal dominant neurodegenerative condition caused by expansions of more than 35 uninterrupted CAG repeats in exon 1 of the huntingtin gene. The CAG repeats in HD and the other seven known diseases caused by CAG codon expansions are translated into long polyglutamine tracts that confer a deleterious gain of function on the mutant proteins. Intraneuronal inclusions comprising aggregates of the relevant mutant proteins are found in the brains of patients with HD and related diseases. It is crucial to determine whether the formation of inclusions is directly pathogenic, because a number of studies have suggested that aggregates may be epiphenomena or even protective. Here, we show that fragments of the bacterial chaperone GroEL and the full-length yeast heat shock protein Hsp104 reduce both aggregate formation and cell death in mammalian cell models of HD, consistent with a causal link between aggregation and pathology. PMID:10920207

  13. Dynamics of nitrifying bacterial communities in the Seine river and estuary as affected by changes in the treatment of Paris wastewater : a comparison of 2001-2003 vs 2012-2013 periods

    NASA Astrophysics Data System (ADS)

    Aissa Grouz, Najla; Billen, Gilles; Garnier, Josette; Mercier, Benjamin; Martinez, Anun

    2014-05-01

    The major branch of the Seine river from the confluence with the Marne river to the entrance of the estuary is deeply affected by the release of wastewater from the huge Paris agglomeration. In the first years of 2000, the largest part of the effluents were still discharged at the Seine-Aval (Achères) treatment plant with only a standard, low residence time, activated sludge treatment, thus releasing a high ammonium load. NH4 concentration as high as 7 mgN/l were frequently observed downstream from Paris agglomeration. Cébron et al. (2003, 2005) and Garnier et al. 2007 described in details how this massive reduced nitrogen concentrations triggered the growth of nitrifying bacteria, already present in the upstream Seine and Marne rivers, but also brought in large amount by the effluents of the wastewater treatment plant themselves. The decrease of ammonium concentration was slow, however, and was only completed 200 km downstream, in the upper estuarine area, where it causes a severe oxygen deficiency. Since 2007, important changes occurred in the treatment of nitrogen in the Parisian wastewater purification plants. In 2007, the Seine-Aval plant treated up to 90% of the ammonium contained in wastewater through nitrification, and 30% of the total supply of nitrates is treated by denitrification. These modifications have of course favorably affected the water quality of the Seine river: ammonium concentrations are reduced by a factor of 5 and the area of oxygen depletion in the upstream estuary is no more observed. However, nitrites, still released in the effluents, are a matter of concern for the water quality of the Seine downstream from Paris. Using measurements of potential microbial activities carried out with the same experimental protocol for the 2000-2003 and 2012-2013 periods, we here examine and model the dynamics of ammonium oxidizing and nitrite oxidizing microbial populations before and after the implementation of nitrification treatment of Paris

  14. Characterization of the aggregates formed by various bacterial lipopolysaccharides in solution and upon interaction with antimicrobial peptides.

    PubMed

    Bello, Gianluca; Eriksson, Jonny; Terry, Ann; Edwards, Katarina; Lawrence, M Jayne; Barlow, David; Harvey, Richard D

    2015-01-20

    The biophysical analysis of the aggregates formed by different chemotypes of bacterial lipopolysaccharides (LPS) before and after challenge by two different antiendotoxic antimicrobial peptides (LL37 and bovine lactoferricin) was performed in order to determine their effect on the morphology of LPS aggregates. Small-angle neutron scattering (SANS) and cryogenic transmission electron microscopy (cryoTEM) were used to examine the structures formed by both smooth and rough LPS chemotypes and the effect of the peptides, by visualization of the aggregates and analysis of the scattering data by means of both mathematical approximations and defined models. The data showed that the structure of LPS determines the morphology of the aggregates and influences the binding activity of both peptides. The morphologies of the worm-like micellar aggregates formed by the smooth LPS were relatively unaltered by the presence of the peptides due to their pre-existing high degree of positive curvature being little affected by their association with either peptide. On the other hand, the aggregates formed by the rough LPS chemotypes showed marked morphological changes from lamellar structures to ordered micellar networks, induced by the increase in positive curvature engendered upon association with the peptides. The combined use of cryoTEM and SANS proved to be a very useful tool for studying the aggregation properties of LPS in solution at biologically relevant concentrations.

  15. The Role of Thin Aggregative Fimbriae on Pathogenic Bacterial Transport Through Porous Media

    NASA Astrophysics Data System (ADS)

    Salvucci, A. E.; Fuka, D. R.; Marjerison, R. D.; Hay, A. G.; Zhang, W.; Caballero, L. A.; Zevi, Y.; Richards, B. K.; Steenhuis, T. S.

    2008-05-01

    Pathogenic bacteria, such as Escherichia coli and Salmonella sp., are responsible for many deaths worldwide every year. Their survival in the natural environment is enhanced by the production of biofilms, which provide a resistance to environmental stresses. However, it remains unclear how these biofilms affect the bacterias' ability to move through the soil matrix and potentially contaminate groundwater or water from drainage systems. In this presentation, we discuss the role of thin aggregative fimbriae (curli), a key biofilm component, on transport through porous media. An experiment was performed consisting of 96 sand columns created using a deep-well microtiter plate. We used well-characterized strains of E. coli, one with the ability to form curli and one without. Pulsing the E. coli strains through the sand column, mimicking natural leaching processes, showed less transport, by greater retention, in the strains that produce curli versus those strains that do not. In addition, when cultured in conditions unfavorable to curli production, transport between strains did not differ significantly. These preliminary results indicate that curli, and to a larger extent biofilms, could be an important component influencing the transport of bacterial strains through the soil matrix. This determination of pathogens' ability to move through the environment, as related to how well they form biofilms, will facilitate a better understanding of the fate of pathogenic bacteria in the environment.

  16. Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study.

    PubMed

    Yoo, Jun Sang; Chang, Seok-Woo; Oh, So Ram; Perinpanayagam, Hiran; Lim, Sang-Min; Yoo, Yeon-Jee; Oh, Yeo-Rok; Woo, Sang-Bin; Han, Seung-Hyun; Zhu, Qiang; Kum, Kee-Yeon

    2014-12-01

    The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA-PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

  17. Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study

    PubMed Central

    Yoo, Jun Sang; Chang, Seok-Woo; Oh, So Ram; Perinpanayagam, Hiran; Lim, Sang-Min; Yoo, Yeon-Jee; Oh, Yeo-Rok; Woo, Sang-Bin; Han, Seung-Hyun; Zhu, Qiang; Kum, Kee-Yeon

    2014-01-01

    The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization. PMID:25012869

  18. Understanding Nitrifier Denitrification: How far are we?

    NASA Astrophysics Data System (ADS)

    Wrage-Mönnig, N.

    2014-12-01

    Nitrifier denitrification is the oxidation of ammonia (NH3) via hydroxylamine (NH2OH) to nitrite (NO2-) and subsequent reduction of NO2- via nitric oxide (NO) to the greenhouse gas nitrous oxide (N2O) and possibly to dinitrogen (N2) by autotrophic nitrifiers. Especially in recent years, a lot of research has been conducted on this pathway. Under some conditions, it might dominate the N2O production from soils. Methods for studying nitrifier denitrification include selective inhibition, stable isotope and isotopomer methods, molecular and modelling approaches. They are applied from pure culture and pot studies to the field scale, trying to improve our knowledge of the conditions and factors controlling nitrifier denitrification. But how far are we? What have we learned so far and what remains to be discovered? With this contribution, I am trying to give an update of our understanding of this less well-known but important pathway.

  19. Diversity study of nitrifying bacteria in full-scale municipal wastewater treatment plants.

    PubMed

    Siripong, Slil; Rittmann, Bruce E

    2007-03-01

    We hypothesize that activated-sludge processes having stable and complete nitrification have significant and similar diversity and functional redundancy among its ammonia- and nitrite-oxidizing bacteria, despite differences in temperature, solids retention time (SRT), and other operating conditions. To evaluate this hypothesis, we examined the diversity of nitrifying bacterial communities in all seven water-reclamation plants (WRPs) operated by Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). These plants vary in types of influent waste stream, plant size, water temperature, and SRT. We used terminal restriction fragment length polymorphism (T-RFLP) targeting the 16S rRNA gene and group-specific ammonia-monooxygenase functional gene (amoA) to investigate these hard-to-culture nitrifying bacteria in the full-scale WRPs. We demonstrate that nitrifying bacteria carrying out the same metabolism coexist in all WRPs studied. We found ammonia-oxidizing bacteria (AOB) belonging to the Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrosomonas communis, and Nitrosospira lineages in all plants. We also observed coexisting Nitrobacter and Nitrospira genera for nitrite-oxidizing bacteria (NOB). Among the factors that varied among the WRPs, only the seasonal temperature variation seemed to change the nitrifying community, especially the balance between Nitrosospira and Nitrosomonas, although both coexisted in winter and summer samples. The coexistence of various nitrifiers in all WRPs is evidence of functional redundancy, a feature that may help maintain the stability of the system for nitrification.

  20. Pyrosequencing-based assessment of soil bacterial communities within soil aggregates: Linking structure to C storage

    USDA-ARS?s Scientific Manuscript database

    Alterations in soil structural properties created by agricultural management practices have a significant influence on soil aggregation, which manages the chemical and physical heterogeneity of soil properties, and, consequently, the distribution of microorganisms and their activity among aggregates...

  1. Nitrification and growth of autotrophic nitrifying bacteria and Thaumarchaeota in the coastal North Sea

    NASA Astrophysics Data System (ADS)

    Veuger, Bart; Pitcher, Angela; Schouten, Stefan; Sinninghe Damsté, Jaap S.; Middelburg, Jack J.

    2013-04-01

    A dual stable isotope (15N and 13C) tracer approach in combination with compound-specific stable isotope analysis of bacterial and Thaumarchaeotal lipid biomarkers was used to investigate nitrification and the associated growth of autotrophic nitrifiers in the Dutch coastal North Sea. This study focusses on the stoichiometry between nitrification and DIC fixation by autotrophic nitrifiers as well as on the contributions of bacteria versus Thaumarchaeota to total autotrophic DIC-fixation by nitrifiers. Water from the dutch coastal North Sea was collected at weekly to biweekly intervals during the winter of 2007-2008. Watersamples were incubated with 15N-labeled ammonium and 15N was traced into nitrate and suspended material to quantify rates of nitrification and ammonium assimilation respectively. Growth of autotrophic nitrifiers was measured by incubating water samples with 13C-DIC in the presence and absence of nitrification inhibitors (nitrapyrin and chlorate) and subsequent analysis of 13C in bacterial phospholipid-derived fatty acids (PLFAs) and the Thaumarchaeotal biomarker crenarchaeol. Results revealed high nitrification rates with nitrification being the primary sink for ammonium. 13C-DIC fixation into bacterial and Thaumarchaeotal lipids was strongly reduced by the nitrification inhibitors (27-95%). The ratio between rates of nitrification versus DIC fixation by nitrifiers was higher or even much higher than typical values for autotrophic nitrifiers, indicating that little DIC was fixed relative to the amount of energy that was generated by nitrification, and hence that other other processes for C acquisition may have been relevant as well. The inhibitor-sensitive 13C-PLFA pool was dominated by the common PLFAs 16:0, 16:1ω7c and 18:1ω7c throughout the whole sampling period and occasionally also included the polyunsaturated fatty acids 18:2ω6c and 18:3ω3. Cell-specific 13C-DIC fixation activity of the nitrifying bacteria was much higher than that of the

  2. Adherent-Invasive Escherichia coli Production of Cellulose Influences Iron-Induced Bacterial Aggregation, Phagocytosis, and Induction of Colitis

    PubMed Central

    Ellermann, Melissa; Huh, Eun Young; Liu, Bo; Carroll, Ian M.; Tamayo, Rita

    2015-01-01

    Adherent-invasive Escherichia coli (AIEC), a functionally distinct subset of resident intestinal E. coli associated with Crohn's disease, is characterized by enhanced epithelial adhesion and invasion, survival within macrophages, and biofilm formation. Environmental factors, such as iron, modulate E. coli production of extracellular structures, which in turn influence the formation of multicellular communities, such as biofilms, and bacterial interactions with host cells. However, the physiological and functional responses of AIEC to variable iron availability have not been thoroughly investigated. We therefore characterized the impact of iron on the physiology of AIEC strain NC101 and subsequent interactions with macrophages. Iron promoted the cellulose-dependent aggregation of NC101. Bacterial cells recovered from the aggregates were more susceptible to phagocytosis than planktonic cells, which corresponded with the decreased macrophage production of the proinflammatory cytokine interleukin-12 (IL-12) p40. Prevention of aggregate formation through the disruption of cellulose production reduced the phagocytosis of iron-exposed NC101. In contrast, under iron-limiting conditions, where NC101 aggregation is not induced, the disruption of cellulose production enhanced NC101 phagocytosis and decreased macrophage secretion of IL-12 p40. Finally, abrogation of cellulose production reduced NC101 induction of colitis when NC101 was monoassociated in inflammation-prone Il10−/− mice. Taken together, our results introduce cellulose as a novel physiological factor that impacts host-microbe-environment interactions and alters the proinflammatory potential of AIEC. PMID:26216423

  3. Sealing efficacy of mineral trioxide aggregate with and without nanosilver for root end filling: An in vitro bacterial leakage study

    PubMed Central

    Eskandarinezhad, Mahsa; Sharghi, Reza; Shirazi, Sajjad; Shakouie, Sahar; Milani, Amin-Salem; Balaei, Esrafil

    2017-01-01

    Background Various materials have been added to mineral trioxide aggregate to enhance its properties. This study was aimed to compare the sealing efficacy of MTA with and without nanosilver using bacterial leakage approach. Material and Methods Seventy canine teeth were prepared and obturated. Then, after apical resection, the root-end cavities were prepared by ultrasonic retrotips. Teeth were randomly divided into 4 groups containing two experimental groups (n=30) and two negative and positive controls (n=5). In group 1 and 2, root-end cavities were respectively filled with MTA and MTA with nanosilver (by 1% weight). Leakage assessment was carried out by bacterial leakage apparatus with Enterococcus faecalis species. Leakage comparison between experimental groups was done using Mann-Whitney test by Spss 16 software at significancy level of 0.05. Results The median bacterial leakages for MTA and MTA with nanosilver were 19 and 2, respectively. The mean bacterial leakages for MTA and MTA with nanosilver were 30.06±28.67 and 9.66±14.25, respectively. Mann-Whitney test indicated that there was a significant difference in bacterial leakage day between two experimental groups (P=0.002). Conclusions Based on the findings of this in-vitro bacterial leakage study, adding nanosilver to MTA decreased its sealing ability. Key words:Root canal therapy, root canal obturation, root canal filling materials, nanosilver, MTA. PMID:28149459

  4. Sealing efficacy of mineral trioxide aggregate with and without nanosilver for root end filling: An in vitro bacterial leakage study.

    PubMed

    Eskandarinezhad, Mahsa; Shahveghar-Asl, Naiemeh; Sharghi, Reza; Shirazi, Sajjad; Shakouie, Sahar; Milani, Amin-Salem; Balaei, Esrafil

    2017-01-01

    Various materials have been added to mineral trioxide aggregate to enhance its properties. This study was aimed to compare the sealing efficacy of MTA with and without nanosilver using bacterial leakage approach. Seventy canine teeth were prepared and obturated. Then, after apical resection, the root-end cavities were prepared by ultrasonic retrotips. Teeth were randomly divided into 4 groups containing two experimental groups (n=30) and two negative and positive controls (n=5). In group 1 and 2, root-end cavities were respectively filled with MTA and MTA with nanosilver (by 1% weight). Leakage assessment was carried out by bacterial leakage apparatus with Enterococcus faecalis species. Leakage comparison between experimental groups was done using Mann-Whitney test by Spss 16 software at significancy level of 0.05. The median bacterial leakages for MTA and MTA with nanosilver were 19 and 2, respectively. The mean bacterial leakages for MTA and MTA with nanosilver were 30.06±28.67 and 9.66±14.25, respectively. Mann-Whitney test indicated that there was a significant difference in bacterial leakage day between two experimental groups (P=0.002). Based on the findings of this in-vitro bacterial leakage study, adding nanosilver to MTA decreased its sealing ability. Key words:Root canal therapy, root canal obturation, root canal filling materials, nanosilver, MTA.

  5. Influence of microbial community structure of seed sludge on the properties of aerobic nitrifying granules.

    PubMed

    Song, Zhiwei; Li, Ting; Wang, Qiuxu; Pan, Yu; Li, Lixin

    2015-09-01

    In order to evaluate the influence of microbial community structure of seed sludge on the properties of aerobic nitrifying granules, these granules were cultivated with different seed sludge, and the variation of microbial community and dominant bacterial groups that impact the nitrogen removal efficiency of the aerobic nitrifying granules were analyzed and identified using 16s rDNA sequence and denaturing gradient gel electrophoresis (DGGE) profiles. The results presented here demonstrated that the influence of the community structure of seed sludge on the properties of aerobic nitrifying granules was remarkable, and the granules cultivated by activated sludge from a beer wastewater treatment plant showed better performance, with a stable sludge volume index (SVI) value of 20mL/g, high extracellular polymeric substance (EPS) content of 183.3mg/L, high NH4(+)-N removal rate of 89.42% and abundant microbial population with 10 dominant bacterial groups. This indicated that activated sludge with abundant communities is suitable for use as seed sludge in culturing aerobic nitrifying granules. Copyright © 2015. Published by Elsevier B.V.

  6. Transcriptional response of nitrifying communities to wetting of dry soil.

    PubMed

    Placella, Sarah A; Firestone, Mary K

    2013-05-01

    The first rainfall following a severe dry period provides an abrupt water potential change that is both an acute physiological stress and a defined stimulus for the reawakening of soil microbial communities. We followed the responses of indigenous communities of ammonia-oxidizing bacteria, ammonia-oxidizing archaea, and nitrite-oxidizing bacteria to the addition of water to laboratory incubations of soils taken from two California annual grasslands following a typically dry Mediterranean summer. By quantifying transcripts for a subunit of bacterial and archaeal ammonia monooxygenases (amoA) and a bacterial nitrite oxidoreductase (nxrA) in soil from 15 min to 72 h after water addition, we identified transcriptional response patterns for each of these three groups of nitrifiers. An increase in quantity of bacterial amoA transcripts was detectable within 1 h of wet-up and continued until the size of the ammonium pool began to decrease, reflecting a possible role of transcription in upregulation of nitrification after drought-induced stasis. In one soil, the pulse of amoA transcription lasted for less than 24 h, demonstrating the transience of transcriptional pools and the tight coupling of transcription to the local soil environment. Analysis of 16S rRNA using a high-density microarray suggested that nitrite-oxidizing Nitrobacter spp. respond in tandem with ammonia-oxidizing bacteria while nitrite-oxidizing Nitrospina spp. and Nitrospira bacteria may not. Archaeal ammonia oxidizers may respond slightly later than bacterial ammonia oxidizers but may maintain elevated transcription longer. Despite months of desiccation-induced inactivation, we found rapid transcriptional response by all three groups of soil nitrifiers.

  7. Influence of fullerene (C60) on soil bacterial communities: aqueous aggregate size and solvent co-introduction effects

    PubMed Central

    Tong, Zhong-Hua; Bischoff, Marianne; Nies, Loring F.; Carroll, Natalie J.; Applegate, Bruce; Turco, Ronald F.

    2016-01-01

    Fullerene C60 nanoparticles are being used in broad range of applications. It is important to assess their potential impacts in the environment. We evaluated the effects of C60 introduced as aqueous suspensions of nC60 aggregates of different particle size or via organic solvents on soils with different organic matter contents in this study. Impacts of the application were evaluated by measuring total microbial biomass, metabolic activity and bacterial community structure. Results show that nC60 aggregates, introduced as an aqueous suspension, had size-dependent effects on soil bacterial community composition in the low organic matter system, but induced minimal change in the microbial biomass and metabolic activity in soils with both high and low organic matter contents. Fullerene C60, co-introduced via an organic solvent, did not influence the response of soil microbes to the organic solvents. Our results suggest that nC60 aggregates of smaller size may have negative impact on soil biota and soil organic matter may play a key role in modulating the environmental effect of nanomaterials. PMID:27306076

  8. Influence of fullerene (C60) on soil bacterial communities: aqueous aggregate size and solvent co-introduction effects.

    PubMed

    Tong, Zhong-Hua; Bischoff, Marianne; Nies, Loring F; Carroll, Natalie J; Applegate, Bruce; Turco, Ronald F

    2016-06-16

    Fullerene C60 nanoparticles are being used in broad range of applications. It is important to assess their potential impacts in the environment. We evaluated the effects of C60 introduced as aqueous suspensions of nC60 aggregates of different particle size or via organic solvents on soils with different organic matter contents in this study. Impacts of the application were evaluated by measuring total microbial biomass, metabolic activity and bacterial community structure. Results show that nC60 aggregates, introduced as an aqueous suspension, had size-dependent effects on soil bacterial community composition in the low organic matter system, but induced minimal change in the microbial biomass and metabolic activity in soils with both high and low organic matter contents. Fullerene C60, co-introduced via an organic solvent, did not influence the response of soil microbes to the organic solvents. Our results suggest that nC60 aggregates of smaller size may have negative impact on soil biota and soil organic matter may play a key role in modulating the environmental effect of nanomaterials.

  9. Influence of fullerene (C60) on soil bacterial communities: aqueous aggregate size and solvent co-introduction effects

    NASA Astrophysics Data System (ADS)

    Tong, Zhong-Hua; Bischoff, Marianne; Nies, Loring F.; Carroll, Natalie J.; Applegate, Bruce; Turco, Ronald F.

    2016-06-01

    Fullerene C60 nanoparticles are being used in broad range of applications. It is important to assess their potential impacts in the environment. We evaluated the effects of C60 introduced as aqueous suspensions of nC60 aggregates of different particle size or via organic solvents on soils with different organic matter contents in this study. Impacts of the application were evaluated by measuring total microbial biomass, metabolic activity and bacterial community structure. Results show that nC60 aggregates, introduced as an aqueous suspension, had size-dependent effects on soil bacterial community composition in the low organic matter system, but induced minimal change in the microbial biomass and metabolic activity in soils with both high and low organic matter contents. Fullerene C60, co-introduced via an organic solvent, did not influence the response of soil microbes to the organic solvents. Our results suggest that nC60 aggregates of smaller size may have negative impact on soil biota and soil organic matter may play a key role in modulating the environmental effect of nanomaterials.

  10. Anti-Pseudomonas aeruginosa IgY Antibodies Induce Specific Bacterial Aggregation and Internalization in Human Polymorphonuclear Neutrophils.

    PubMed

    Thomsen, K; Christophersen, L; Bjarnsholt, T; Jensen, P Ø; Moser, C; Høiby, N

    2015-07-01

    Polymorphonuclear neutrophils (PMNs) are essential cellular constituents in the innate host response, and their recruitment to the lungs and subsequent ubiquitous phagocytosis controls primary respiratory infection. Cystic fibrosis pulmonary disease is characterized by progressive pulmonary decline governed by a persistent, exaggerated inflammatory response dominated by PMNs. The principal contributor is chronic Pseudomonas aeruginosa biofilm infection, which attracts and activates PMNs and thereby is responsible for the continuing inflammation. Strategies to prevent initial airway colonization with P. aeruginosa by augmenting the phagocytic competence of PMNs may postpone the deteriorating chronic biofilm infection. Anti-P. aeruginosa IgY antibodies significantly increase the PMN-mediated respiratory burst and subsequent bacterial killing of P. aeruginosa in vitro. The mode of action is attributed to IgY-facilitated formation of immobilized bacteria in aggregates, as visualized by fluorescence microscopy and the induction of increased bacterial hydrophobicity. Thus, the present study demonstrates that avian egg yolk immunoglobulins (IgY) targeting P. aeruginosa modify bacterial fitness, which enhances bacterial killing by PMN-mediated phagocytosis and thereby may facilitate a rapid bacterial clearance in airways of people with cystic fibrosis. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  11. Anti-Pseudomonas aeruginosa IgY Antibodies Induce Specific Bacterial Aggregation and Internalization in Human Polymorphonuclear Neutrophils

    PubMed Central

    Thomsen, K.; Christophersen, L.; Bjarnsholt, T.; Jensen, P. Ø.; Moser, C.

    2015-01-01

    Polymorphonuclear neutrophils (PMNs) are essential cellular constituents in the innate host response, and their recruitment to the lungs and subsequent ubiquitous phagocytosis controls primary respiratory infection. Cystic fibrosis pulmonary disease is characterized by progressive pulmonary decline governed by a persistent, exaggerated inflammatory response dominated by PMNs. The principal contributor is chronic Pseudomonas aeruginosa biofilm infection, which attracts and activates PMNs and thereby is responsible for the continuing inflammation. Strategies to prevent initial airway colonization with P. aeruginosa by augmenting the phagocytic competence of PMNs may postpone the deteriorating chronic biofilm infection. Anti-P. aeruginosa IgY antibodies significantly increase the PMN-mediated respiratory burst and subsequent bacterial killing of P. aeruginosa in vitro. The mode of action is attributed to IgY-facilitated formation of immobilized bacteria in aggregates, as visualized by fluorescence microscopy and the induction of increased bacterial hydrophobicity. Thus, the present study demonstrates that avian egg yolk immunoglobulins (IgY) targeting P. aeruginosa modify bacterial fitness, which enhances bacterial killing by PMN-mediated phagocytosis and thereby may facilitate a rapid bacterial clearance in airways of people with cystic fibrosis. PMID:25895968

  12. Nitrification and growth of autotrophic nitrifying bacteria and Thaumarchaeota in the coastal North Sea

    NASA Astrophysics Data System (ADS)

    Veuger, B.; Pitcher, A.; Schouten, S.; Sinninghe Damsté, J. S.; Middelburg, J. J.

    2013-03-01

    Nitrification and the associated growth of autotrophic nitrifiers, as well as the contributions of bacteria and Thaumarchaeota to total autotrophic C-fixation by nitrifiers were investigated in the Dutch coastal North Sea from October 2007 to March 2008. Rates of nitrification were determined by incubation of water samples with 15N-ammonium and growth of autotrophic nitrifiers was measured by incubation with 13C-DIC (dissolved inorganic carbon) in the presence and absence of nitrification inhibitors (nitrapyrin and chlorate) in combination with compound-specific stable isotope (13C) analysis of bacterial and Thaumarchaeotal lipid biomarkers. Net nitrification during the sampling period was evident from the concentration dynamics of ammonium, nitrite and nitrate. Measured nitrification rates were high (41-221 nmol N L-1 h-1). Ammonium assimilation was always substantially lower than nitrification - with nitrification on average contributing 89% (range 73-97%) to total ammonium consumption. 13C-DIC fixation into bacterial and Thaumarchaeotal lipids was strongly reduced by the nitrification inhibitors (27-95 %). The inhibitor-sensitive 13C-PLFA (phospholipid-derived fatty acid) pool was dominated by the common PLFAs 16:0, 16:1ω7c and 18:1ω7c throughout the whole sampling period and occasionally also included the polyunsaturated fatty acids 18:2ω6c and 18:3ω3. 13C-DIC fixation activity of the nitrifying bacteria was much higher than that of the nitrifying Thaumarchaeota throughout the whole sampling period, even during the peak in Thaumarchaeotal abundance and activity. This suggests that the contribution of autotrophic Thaumarchaeota to nitrification during winter in the coastal North Sea may have been smaller than expected from their gene abundance (16S rRNA and amoA (ammonia monooxygenase)). These results emphasize the importance of direct measurements of the actual activity of bacteria and Thaumarchaeota, rather than abundance measurements only, in order to

  13. Purification of saliva agglutinin of Streptococcus intermedius and its association with bacterial aggregation and adherence.

    PubMed

    Yamaguchi, Taihei

    2004-02-01

    Streptococcus intermedius strain 1208-1 cells were aggregated in the presence of saliva. The saliva agglutinin was purified by centrifugation, filtration, and gel filtration. SDS-PAGE analyses indicated that the purified agglutinin consisted of two high-molecular-mass proteins. Aggregation was dependent on calcium over pH 5.5, with 1 mM being the most effective concentration. Boiling inactivated purified agglutinin. S. intermedius strain 3 and Streptococcus mutans strain 1 were aggregated in the purified agglutinin. After adsorption with strain 1208-1 cells, the saliva sample did not exhibit any aggregation activity, and the agglutinin bands were no longer visible by SDS-PAGE. Adherence analyses demonstrated that the purified agglutinin immobilized on the surfaces of polystyrene wells, actinomyces cells, and apatite beads accounted for the binding of streptococcus cells. Agglutinin also effectively inhibited adherence to apatite beads coated with native saliva.

  14. The influence of ligand valency on aggregation mechanisms for inhibiting bacterial toxins.

    PubMed

    Sisu, Cristina; Baron, Andrew J; Branderhorst, Hilbert M; Connell, Simon D; Weijers, Carel A G M; de Vries, Renko; Hayes, Edward D; Pukin, Aliaksei V; Gilbert, Michel; Pieters, Roland J; Zuilhof, Han; Visser, Gerben M; Turnbull, W Bruce

    2009-01-26

    Divalent and tetravalent analogues of ganglioside GM1 are potent inhibitors of cholera toxin and Escherichia coli heat-labile toxin. However, they show little increase in inherent affinity when compared to the corresponding monovalent carbohydrate ligand. Analytical ultracentrifugation and dynamic light scattering have been used to demonstrate that the multivalent inhibitors induce protein aggregation and the formation of space-filling networks. This aggregation process appears to arise when using ligands that do not match the valency of the protein receptor. While it is generally accepted that multivalency is an effective strategy for increasing the activity of inhibitors, here we show that the valency of the inhibitor also has a dramatic effect on the kinetics of aggregation and the stability of intermediate protein complexes. Structural studies employing atomic force microscopy have revealed that a divalent inhibitor induces head-to-head dimerization of the protein toxin en route to higher aggregates.

  15. Differential responses of nitrifying archaea and bacteria to methylene blue toxicity.

    PubMed

    Sipos, A J; Urakawa, H

    2016-02-01

    Methylene blue, a heterocyclic aromatic chemical compound used to treat fish diseases in the ornamental fish aquaculture industry, is believed to impair nitrification as a side effect. However, very little is known about the toxicity of methylene blue to nitrifying micro-organisms. Here, we report the susceptibility of six bacterial and one archaeal ammonia-oxidizing micro-organisms to methylene blue within the range of 10 ppb to 10 ppm. Remarkably high susceptibility was observed in the archaeal species Nitrosopumilus maritimus compared to the bacterial species. Ammonia oxidation by Nitrosopumilus maritimus was inhibited 65% by 10 ppb of methylene blue. Of the bacterial species examined, Nitrosococcus oceani was the most resistant to methylene blue toxicity. For similar inhibition of Nitrosococcus oceani (75% inhibition), one thousand times more methylene blue (10 ppm) was needed. The examination of single cell viability on Nitrosomonas marina demonstrated that methylene blue is lethal to the cells rather than reducing their single cell ammonia oxidation activity. The level of susceptibility to methylene blue was related to the cell volume, intracytoplasmic membrane arrangement and the evolutionary lineage of nitrifying micro-organisms. Our findings are relevant for effectively using methylene blue in various aquaculture settings by helping minimize its impact on nitrifiers during the treatment of fish diseases. In the future, resistant nitrifiers such as Nitrosococcus oceani may be purposely added to aquaculture systems to maintain nitrification activity during treatments with methylene blue. The susceptibility of six bacterial and one archaeal nitrifying micro-organisms to methylene blue was tested. Remarkably high susceptibility was observed in the archaeal species compared to the bacterial species. The level of resistance to methylene blue was related to the cell volume, cytomembrane system and the taxonomic position of the nitrifying micro

  16. Aggregate formation in a freshwater bacterial strain induced by growth state and conspecific chemical cues.

    PubMed

    Blom, Judith F; Horňák, Karel; Simek, Karel; Pernthaler, Jakob

    2010-09-01

    We investigated the induction of aggregate formation in the freshwater bacterium Sphingobium sp. strain Z007 by growth state and protistan grazing. Dialysis bag batch culture experiments were conducted in which these bacteria were grown spatially separated from bacteria or from co-cultures of bacteria and predators. In pure cultures of Sphingobium sp. strain Z007, the concentrations of single cells and aggregates inside and outside the dialysis membranes developed in a similar manner over 3 days of incubation, and the proportions of aggregates were highest during the exponential growth phase. Cell production of Sphingobium sp. strain Z007 was enhanced in the presence of another isolate, Limnohabitans planktonicus, from an abundant freshwater lineage (R-BT065) outside the bags, and even more so if that strain was additionally grazed upon by the bacterivorous flagellate Poterioochromonas sp. However, the ratios of single cells to aggregates of Sphingobium sp. strain Z007 were not affected in either case. By contrast, the feeding of flagellates on Sphingobium sp. strain Z007 outside the dialysis bags led to significantly higher proportions of aggregates inside the bags. This was not paralleled by an increase in growth rates, and all cultures were in a comparable growth state at the end of the experiment. We conclude that two mechanisms, growth state and the possible release of infochemicals by the predator, may induce aggregate formation of Sphingobium sp. strain Z007. Moreover, these infochemicals only appeared to be generated by predation on cells from the same species.

  17. Nitrification and growth of autotrophic nitrifying bacteria and Thaumarchaeota in the coastal North Sea

    NASA Astrophysics Data System (ADS)

    Veuger, B.; Pitcher, A.; Schouten, S.; Sinninghe Damsté, J. S.; Middelburg, J. J.

    2012-11-01

    Nitrification and the associated growth of autotrophic nitrifiers, as well as the contributions of bacteria and Thaumarchaeota to total autotrophic C-fixation by nitrifiers were investigated in the Dutch coastal North Sea from October 2007 to March 2008. Rates of nitrification were determined by incubation of water samples with 15N-ammonium and growth of autotrophic nitrifiers was measured by incubation with 13C-DIC in the presence and absence of nitrification inhibitors (nitrapyrin and chlorate) in combination with compound-specific stable isotope (13C) analysis of bacterial- and Thaumarchaeotal lipid biomarkers. Net nitrification during the sampling period was evident from the concentration dynamics of ammonium, nitrite and nitrate. Measured nitrification rates were high (41-221 nmol N l-1h-1). Ammonium assimilation was always substantially lower than nitrification with nitrification on average contributing 89% (range 73-97%) to total ammonium consumption. 13C-DIC fixation into bacterial and Thaumarchaeotal lipids was strongly reduced by the nitrification inhibitors (27-95%). The inhibitor-sensitive 13C-PLFA pool was dominated by the common PLFAs 16:0, 16:1ω7c and 18:1ω7c throughout the whole sampling period and occasionally also included the polyunsaturated fatty acids 18:2ω6c and 18:3ω3. Cell-specific 13C-DIC fixation activity of the nitrifying bacteria was much higher than that of the nitrifying Thaumarchaeota throughout the whole sampling period, even during the peak in Thaumarchaeotal abundance and activity. This suggests that the contribution of autotrophic Thaumarchaeota to nitrification during winter in the coastal North Sea may have been smaller than expected from their gene abundance. These results emphasize the importance of direct measurements of the actual activity of bacteria and Thaumarchaeota, rather than abundance measurements only, in order to elucidate their biogeochemical importance. The ratio between rates of nitrification versus DIC

  18. Biological role of bacterial inclusion bodies: a model for amyloid aggregation.

    PubMed

    García-Fruitós, Elena; Sabate, Raimon; de Groot, Natalia S; Villaverde, Antonio; Ventura, Salvador

    2011-07-01

    Inclusion bodies are insoluble protein aggregates usually found in recombinant bacteria when they are forced to produce heterologous protein species. These particles are formed by polypeptides that cross-interact through sterospecific contacts and that are steadily deposited in either the cell's cytoplasm or the periplasm. An important fraction of eukaryotic proteins form inclusion bodies in bacteria, which has posed major problems in the development of the biotechnology industry. Over the last decade, the fine dissection of the quality control system in bacteria and the recognition of the amyloid-like architecture of inclusion bodies have provided dramatic insights on the dynamic biology of these aggregates. We discuss here the relevant aspects, in the interface between cell physiology and structural biology, which make inclusion bodies unique models for the study of protein aggregation, amyloid formation and prion biology in a physiologically relevant background. © 2011 The Authors Journal compilation © 2011 FEBS.

  19. Cyanate as an energy source for nitrifiers.

    PubMed

    Palatinszky, Marton; Herbold, Craig; Jehmlich, Nico; Pogoda, Mario; Han, Ping; von Bergen, Martin; Lagkouvardos, Ilias; Karst, Søren M; Galushko, Alexander; Koch, Hanna; Berry, David; Daims, Holger; Wagner, Michael

    2015-08-06

    Ammonia- and nitrite-oxidizing microorganisms are collectively responsible for the aerobic oxidation of ammonia via nitrite to nitrate and have essential roles in the global biogeochemical nitrogen cycle. The physiology of nitrifiers has been intensively studied, and urea and ammonia are the only recognized energy sources that promote the aerobic growth of ammonia-oxidizing bacteria and archaea. Here we report the aerobic growth of a pure culture of the ammonia-oxidizing thaumarchaeote Nitrososphaera gargensis using cyanate as the sole source of energy and reductant; to our knowledge, the first organism known to do so. Cyanate, a potentially important source of reduced nitrogen in aquatic and terrestrial ecosystems, is converted to ammonium and carbon dioxide in Nitrososphaera gargensis by a cyanase enzyme that is induced upon addition of this compound. Within the cyanase gene family, this cyanase is a member of a distinct clade also containing cyanases of nitrite-oxidizing bacteria of the genus Nitrospira. We demonstrate by co-culture experiments that these nitrite oxidizers supply cyanase-lacking ammonia oxidizers with ammonium from cyanate, which is fully nitrified by this microbial consortium through reciprocal feeding. By screening a comprehensive set of more than 3,000 publically available metagenomes from environmental samples, we reveal that cyanase-encoding genes clustering with the cyanases of these nitrifiers are widespread in the environment. Our results demonstrate an unexpected metabolic versatility of nitrifying microorganisms, and suggest a previously unrecognized importance of cyanate in cycling of nitrogen compounds in the environment.

  20. Comparison of the photosensitivity and bacterial toxicity of spherical and tubular fullerenes of variable aggregate size

    NASA Astrophysics Data System (ADS)

    Chae, So-Ryong; Therezien, Mathieu; Budarz, Jeffrey Farner; Wessel, Lauren; Lin, Shihong; Xiao, Yao; Wiesner, Mark R.

    2011-10-01

    Nanomaterials such as fullerene C60, carbon nanotubes (CNTs), and other fullerenes show unique electrical, chemical, mechanical, and thermal properties that are not well understood in the context of the environmental behavior of this class of carbon-based materials. In this study, aqueous suspensions of three fullerenes nanoparticles, C60, single-wall (SW) and multi-wall (MW) CNTs were prepared by sonication and tested for reactive oxygen species (ROS) production and inactivation of Vibrio fischeri, a gram-negative rod-shaped bacterium, under ultraviolet (UV)-A irradiation. We show that ROS production and microbial inactivation increases as colloidal aggregates of C60, SWCNT, and MWCNT are fractionated to enrich with smaller aggregates by progressive membrane filtration. As the quantity and influence of these more reactive fractions of the suspension may increase with time and/or as the result of fractionation processes in the laboratory or the environment, experiments evaluating photo-reactivity and toxicity endpoints must take into account the evolution and heterogeneity of nanoparticle aggregates in water.

  1. Cyanate as energy source for nitrifiers

    PubMed Central

    Palatinszky, Marton; Herbold, Craig; Jehmlich, Nico; Pogoda, Mario; Han, Ping; von Bergen, Martin; Lagkouvardos, Ilias; Karst, Søren M.; Galushko, Alexander; Koch, Hanna; Berry, David; Daims, Holger; Wagner, Michael

    2015-01-01

    Ammonia- and nitrite-oxidizers are collectively responsible for the aerobic oxidation of ammonia via nitrite to nitrate and play essential roles for the global biogeochemical nitrogen cycle. The physiology of these nitrifying microbes has been intensively studied since the first experiments of Sergei Winogradsky more than a century ago. Urea and ammonia are the only recognized energy sources that promote the aerobic growth of ammonia-oxidizing bacteria and archaea. Here we report the aerobic growth of a pure culture of the ammonia-oxidizing thaumarchaeote Nitrososphaera gargensis1 on cyanate as the sole source of energy and reductant, the first organism known to do so. Cyanate, which is a potentially important source of reduced nitrogen in aquatic and terrestrial ecosystems2, is converted to ammonium and CO2 by this archaeon using a cyanase that is induced upon addition of this compound. Within the cyanase gene family, this cyanase is a member of a distinct clade that also contains cyanases of nitrite-oxidizing bacteria of the genus Nitrospira. We demonstrate by co-culture experiments that these nitrite-oxidizers supply ammonia-oxidizers lacking cyanase with ammonium from cyanate, which is fully nitrified by this consortium through reciprocal feeding. Screening of a comprehensive set of more than 3,000 publically available metagenomes from environmental samples revealed that cyanase-encoding genes clustering with the cyanases of these nitrifiers are widespread in the environment. Our results demonstrate an unexpected metabolic versatility of nitrifying microbes and suggest a previously unrecognized importance of cyanate for N-cycling in the environment. PMID:26222031

  2. Monochloramine Cometabolism by Nitrifying Biofilm Relevant ...

    EPA Pesticide Factsheets

    Recently, biological monochloramine removal (i.e., cometabolism) by a pure culture ammonia–oxidizing bacteria, Nitrosomonas europaea, and a nitrifying mixed–culture have been shown to increase monochloramine demand. Although important, these previous suspended culture batch kinetic experiments were not representative of drinking water distribution systems where bacteria grow predominantly as biofilm attached to pipe walls or sediments and physiological differences may exist between suspension and biofilm growth. Therefore, the current research was an important next step in extending the previous results to investigate monochloramine cometabolism by biofilm grown in annular reactors under drinking water relevant conditions. Estimated monochloramine cometabolism kinetics were similar to those of ammonia metabolism, and monochloramine cometabolism was a significant loss mechanism (25–40% of the observed monochloramine loss). These results demonstrated that monochloramine cometabolism occurred in drinking water relevant nitrifying biofilm; thus, cometabolism may be a significant contribution to monochloramine loss during nitrification episodes in distribution systems. Investigate whether or not nitrifying biofilm can biologically transform monochloramine under drinking water relevant conditions.

  3. Bacterial leakage in root canals filled with resin-based and mineral trioxide aggregate-based sealers

    PubMed Central

    Razavian, Hamid; Barekatain, Behnaz; Shadmehr, Elham; Khatami, Mahdieh; Bagheri, Fahime; Heidari, Fariba

    2014-01-01

    Background: Sealing ability is one of the most important features of endodontic sealers. The purpose of this in vitro study was to compare the sealing ability of a resin-based sealer with a mineral trioxide aggregate-based sealer. Materials and Methods: A total of 60 single-rooted extracted human teeth were randomly divided into two experimental groups (n = 25) and two control groups (n = 5). After canal preparation and smear layer removal, both groups were obturated with gutta-percha and sealer. Resin-based AH26 sealer was used in the first group and Fillapex® sealer in the second group. Two layers of nail varnish were applied on tooth surfaces except for the apical 2 mm. In the negative control group, nail varnish was applied on the entire surface. The teeth were mounted according to Lima et al. study and then sterilized by ethylene oxide gas. The samples were evaluated for bacterial microleakage using Enterococcus faecalis (ATCC 29212) for 90 days. Data were analyzed by survival test (P < 0.05). Results: Control groups had either immediate leakage or no leakage. The Fillapex® showed significantly higher amounts of microleakage compared with AH26 sealer (P < 0.05) and both groups exhibited significant differences in comparison with control groups. Conclusion: Both sealers had bacterial leakage. Sealing ability of AH26 was significantly higher than that of Fillapex®. PMID:25426153

  4. Bacterial Leakage of Mineral Trioxide Aggregate, Calcium-Enriched Mixture and Biodentine as Furcation Perforation Repair Materials in Primary Molars

    PubMed Central

    Ramazani, Nahid; Sadeghi, Parisa

    2016-01-01

    Introduction: Adequate seal of iatrogenically perforated area within the root canal system can improve the long term treatment prognosis. This in vitro study evaluated the sealing ability of mineral trioxide aggregate (MTA), calcium-enriched mixture (CEM) cement and Biodentine in repair of furcation perforation in primary molars. Methods and Materials: A total of 61 freshly extracted primary mandibular second molars were randomly divided into three groups (n=17) and 10 teeth were put in negative (without perforation, n=5) and positive (perforated without repair, n=5) control groups. Turbidity was used as the criteria of bacterial leakage, when detected in the model of dual-chamber leakage. Data were analyzed using the Chi-Square and Kaplan-Meier survival analysis in SPSS software. The level of significance was set at 0.05. Results: All positive samples showed turbidity, whereas none of the negative samples allowed bacterial leakage. There was no significant difference between the number of turbidity samples in repaired teeth with all test materials (P=0.13). No significant difference was also detected in the mean survival time (P>0.05). Conclusion: CEM cement and Biodentine showed promising results as perforation repair materials and can be recommended as suitable alternatives of MTA for repair of furcation perforation of primary molars. PMID:27471534

  5. Apical Sealing Ability of Mineral Trioxide Aggregate, Intermediate Restorative Material and Calcium Enriched Mixture Cement: A Bacterial Leakage Study

    PubMed Central

    Shahriari, Shahriar; Faramarzi, Farhad; Alikhani, Mohammad-Yousef; Farhadian, Maryam; Hendi, Seyedeh Sareh

    2016-01-01

    Introduction: This in vitro study compared the apical sealing ability of three common root end filling materials namely mineral trioxide aggregate (MTA), intermediate restorative material (IRM) and calcium-enriched mixture (CEM) cement using a bacterial leakage model. Methods and Materials: The study was conducted on 83 single-rooted human teeth. Tooth crowns were cut and root canals were prepared using the step-back technique. Apical 3 mm of the roots were cut and a three-mm-deep cavity was prepared using an ultrasonic instrument. The samples were divided into three groups (n=25) according to the root-end filling material including MTA, IRM and CEM cement. The roots were inserted into cut-end microtubes. After sterilization with ethylene oxide, microtubes were placed in sterile vials containing 10 mL of Brain Heart Infusion (BHI) broth and incubated at 37°C and 0.1 mL of Enterococcus faecalis suspension compatible with 0.5 McFarland standard (1.5×108 cell/ ml), which was refreshed daily. This procedure was continued for 70 days. The data were analyzed using the chi-square, Kruskal-Wallis and log rank tests. The level of significance was set at 0.05. Results: No significant difference was found in bacterial microleakage among three groups; MTA showed slightly (but not significantly) less microleakage than IRM and CEM. However, the difference in the mean time of microleakage was significant among the groups (P<0.04) and in MTA samples leakage occurred in a longer time than CEM (P<0.012). Conclusion: The three tested root end filling materials had equal sealing efficacy for preventing bacterial leakage. PMID:27790267

  6. Interactions of Nitrifying Bacteria and Heterotrophs: Identification of a Micavibrio-Like Putative Predator of Nitrospira spp.

    PubMed Central

    Dolinšek, Jan; Lagkouvardos, Ilias; Wanek, Wolfgang; Wagner, Michael

    2013-01-01

    Chemolithoautotrophic nitrifying bacteria release soluble organic compounds, which can be substrates for heterotrophic microorganisms. The identities of these heterotrophs and the specificities of their interactions with nitrifiers are largely unknown. In this study, we incubated nitrifying activated sludge with 13C-labeled bicarbonate and used stable isotope probing of 16S rRNA to monitor the flow of carbon from uncultured nitrifiers to heterotrophs. To facilitate the identification of heterotrophs, the abundant 16S rRNA molecules from nitrifiers were depleted by catalytic oligonucleotides containing locked nucleic acids (LNAzymes), which specifically cut the 16S rRNA of defined target organisms. Among the 13C-labeled heterotrophs were organisms remotely related to Micavibrio, a microbial predator of Gram-negative bacteria. Fluorescence in situ hybridization revealed a close spatial association of these organisms with microcolonies of nitrite-oxidizing sublineage I Nitrospira in sludge flocs. The high specificity of this interaction was confirmed by confocal microscopy and a novel image analysis method to quantify the localization patterns of biofilm microorganisms in three-dimensional (3-D) space. Other isotope-labeled bacteria, which were affiliated with Thermomonas, colocalized less frequently with nitrifiers and thus were commensals or saprophytes rather than specific symbionts or predators. These results suggest that Nitrospira spp. are subject to bacterial predation, which may influence the abundance and diversity of these nitrite oxidizers and the stability of nitrification in engineered and natural ecosystems. In silico screening of published next-generation sequencing data sets revealed a broad environmental distribution of the uncultured Micavibrio-like lineage. PMID:23335755

  7. Nitrification and Nitrifying Bacteria in the Lower Seine River and Estuary (France)

    PubMed Central

    Cébron, Aurélie; Berthe, Thierry; Garnier, Josette

    2003-01-01

    The Achères wastewater treatment plant, located just downstream of Paris, discharges its effluents into the lower Seine River. The effluents contain large numbers of heterotrophic bacteria, organic matter, and ammonium and are a source of nitrifying bacteria. As a result, degradation of organic matter by heterotrophic bacteria and subsequent oxygen depletion occur immediately downstream of the effluent outlet, whereas nitrifying bacteria apparently need to build up a significant biomass before ammonium oxidation significantly depletes the oxygen. We quantified the potential total nitrifying activity and the potential activities of the ammonia- and nitrite-oxidizing communities along the Seine River. In the summer, the maximum nitrifying activity occurs in the upper freshwater estuary, ∼200 km downstream of Achères. The quantities of nitrifying bacteria, based on amoA gene copy numbers, and of Nitrobacter organisms, based on 16S rRNA gene copy numbers, were correlated with the potential nitrifying activities. The species composition of ammonia-oxidizing bacteria was investigated at two sites: the Triel station just downstream from Achères (km 84) and the Seine freshwater estuary at the Duclair station (km 278). By means of PCR primers targeting the amoA gene, a gene library was created. Phylogenetic analysis revealed that the majority of the analyzed clones at both sites were affiliated with the genus Nitrosomonas. The Nitrosomonas oligotropha- and Nitrosomonas urea-related clones represented nearly 81% of the community of ammonia-oxidizing bacteria at Triel and 60% at Duclair. Two other ammonia-oxidizing clusters of the β subclass of the Proteobacteria, i.e., Nitrosomonas europaea- and Nitrosospira-like bacteria, were found in smaller numbers. The major change in the ammonia-oxidizing community between the two stations along the Seine River-upper estuary continuum was the replacement of the N. oligotropha- and N. urea-related bacteria by the Nitrosospira

  8. Bacteria of the Candidate Phylum TM7 are Prevalent in Acidophilic Nitrifying Sequencing-Batch Reactors

    PubMed Central

    Hanada, Akiko; Kurogi, Takashi; Giang, Nguyen Minh; Yamada, Takeshi; Kamimoto, Yuki; Kiso, Yoshiaki; Hiraishi, Akira

    2014-01-01

    Laboratory-scale acidophilic nitrifying sequencing-batch reactors (ANSBRs) were constructed by seeding with sewage-activated sludge and cultivating with ammonium-containing acidic mineral medium (pH 4.0) with or without a trace amount of yeast extract. In every batch cycle, the pH varied between 2.7 and 4.0, and ammonium was completely converted to nitrate. Attempts to detect nitrifying functional genes in the fully acclimated ANSBRs by PCR with previously designed primers mostly gave negative results. 16S rRNA gene-targeted PCR and a subsequent denaturating gradient gel electrophoresis analysis revealed that a marked change occurred in the bacterial community during the overall period of operation, in which members of the candidate phylum TM7 and the class Gammaproteobacteria became predominant at the fully acclimated stage. This result was fully supported by a 16S rRNA gene clone library analysis, as the major phylogenetic groups of clones detected (>5% of the total) were TM7 (33%), Gammaproteobacteria (37%), Actinobacteria (10%), and Alphaproteobacteria (8%). Fluorescence in situ hybridization with specific probes also demonstrated the prevalence of TM7 bacteria and Gammaproteobacteria. These results suggest that previously unknown nitrifying microorganisms may play a major role in ANSBRs; however, the ecophysiological significance of the TM7 bacteria predominating in this process remains unclear. PMID:25241805

  9. Culture-independent detection of "TM7" bacteria in a streptomycin-resistant acidophilic nitrifying process

    NASA Astrophysics Data System (ADS)

    Kurogi, T.; Linh, N. T. T.; Kuroki, T.; Yamada, T.; Hiraishi, A.

    2014-02-01

    Nitrification in biological wastewater treatment processes has been believed for long time to take place under neutral conditions and is inhibited under acidic conditions. However, we previously constructed acidophilic nitrifying sequencing-batch reactors (ANSBRs) being capable of nitrification at < pH 4 and harboring bacteria of the candidate phylum "TM7" as the major constituents of the microbial community. In light of the fact that the 16S rRNA of TM7 bacteria has a highly atypical base substitution possibly responsible for resistance to streptomycin at the ribosome level, this study was undertaken to construct streptomycin-resistant acidophilic nitrifying (SRAN) reactors and to demonstrate whether TM7 bacteria are abundant in these reactors. The SRAN reactors were constructed by seeding with nitrifying sludge from an ANSBR and cultivating with ammonium-containing mineral medium (pH 4.0), to which streptomycin at a concentration of 10, 30 and 50 mg L-1 was added. In all reactors, the pH varied between 2.7 and 4.0, and ammonium was completely converted to nitrate in every batch cycle. PCR-aided denaturing gradient gel electrophoresis (DGGE) targeting 16S rRNA genes revealed that some major clones assigned to TM7 bacteria and Gammaproteobacteria were constantly present during the overall period of operation. Fluorescence in situ hybridization (FISH) with specific oligonucleotide probes also showed that TM7 bacteria predominated in all SRAN reactors, accounting for 58% of the total bacterial population on average. Although the biological significance of the TM7 bacteria in the SRAN reactors are unknown, our results suggest that these bacteria are possibly streptomycin-resistant and play some important roles in the acidophilic nitrifying process.

  10. Culture-independent detection of 'TM7' bacteria in a streptomycin-resistant acidophilic nitrifying process

    SciTech Connect

    Kurogi, T.; Linh, N. T. T.; Kuroki, T.; Yamada, T.; Hiraishi, A.

    2014-02-20

    Nitrification in biological wastewater treatment processes has been believed for long time to take place under neutral conditions and is inhibited under acidic conditions. However, we previously constructed acidophilic nitrifying sequencing-batch reactors (ANSBRs) being capable of nitrification at < pH 4 and harboring bacteria of the candidate phylum 'TM7' as the major constituents of the microbial community. In light of the fact that the 16S rRNA of TM7 bacteria has a highly atypical base substitution possibly responsible for resistance to streptomycin at the ribosome level, this study was undertaken to construct streptomycin-resistant acidophilic nitrifying (SRAN) reactors and to demonstrate whether TM7 bacteria are abundant in these reactors. The SRAN reactors were constructed by seeding with nitrifying sludge from an ANSBR and cultivating with ammonium-containing mineral medium (pH 4.0), to which streptomycin at a concentration of 10, 30 and 50 mg L{sup −1} was added. In all reactors, the pH varied between 2.7 and 4.0, and ammonium was completely converted to nitrate in every batch cycle. PCR-aided denaturing gradient gel electrophoresis (DGGE) targeting 16S rRNA genes revealed that some major clones assigned to TM7 bacteria and Gammaproteobacteria were constantly present during the overall period of operation. Fluorescence in situ hybridization (FISH) with specific oligonucleotide probes also showed that TM7 bacteria predominated in all SRAN reactors, accounting for 58% of the total bacterial population on average. Although the biological significance of the TM7 bacteria in the SRAN reactors are unknown, our results suggest that these bacteria are possibly streptomycin-resistant and play some important roles in the acidophilic nitrifying process.

  11. Nitrifying moving bed biofilm reactor (MBBR) biofilm and biomass response to long term exposure to 1 °C.

    PubMed

    Hoang, V; Delatolla, R; Abujamel, T; Mottawea, W; Gadbois, A; Laflamme, E; Stintzi, A

    2014-02-01

    This study aims to investigate moving bed biofilm reactor (MBBR) nitrification rates, nitrifying biofilm morphology, biomass viability as well as bacterial community shifts during long-term exposure to 1 °C. Long-term exposure to 1 °C is the key operational condition for potential ammonia removal upgrade units to numerous northern region treatment systems. The average laboratory MBBR ammonia removal rate after long-term exposure to 1 °C was measured to be 18 ± 5.1% as compared to the average removal rate at 20 °C. Biofilm morphology and specifically the thickness along with biomass viability at various depths in the biofilm were investigated using variable pressure electron scanning microscope (VPSEM) imaging and confocal laser scanning microscope (CLSM) imaging in combination with viability live/dead staining. The biofilm thickness along with the number of viable cells showed significant increases after long-term exposure to 1 °C. Hence, this study observed nitrifying bacteria with higher activities at warm temperatures and a slightly greater quantity of nitrifying bacteria with lower activities at cold temperatures in nitrifying MBBR biofilms. Using DNA sequencing analysis, Nitrosomonas and Nitrosospira (ammonia oxidizers) as well as Nitrospira (nitrite oxidizer) were identified and no population shift was observed between 20 °C and after long-term exposure to 1 °C.

  12. Exposure to the Functional Bacterial Amyloid Protein Curli Enhances Alpha-Synuclein Aggregation in Aged Fischer 344 Rats and Caenorhabditis elegans

    PubMed Central

    Chen, Shu G.; Stribinskis, Vilius; Rane, Madhavi J.; Demuth, Donald R.; Gozal, Evelyne; Roberts, Andrew M.; Jagadapillai, Rekha; Liu, Ruolan; Choe, Kyonghwan; Shivakumar, Bhooma; Son, Francheska; Jin, Shunying; Kerber, Richard; Adame, Anthony; Masliah, Eliezer; Friedland, Robert P.

    2016-01-01

    Misfolded alpha-synuclein (AS) and other neurodegenerative disorder proteins display prion-like transmission of protein aggregation. Factors responsible for the initiation of AS aggregation are unknown. To evaluate the role of amyloid proteins made by the microbiota we exposed aged rats and transgenic C. elegans to E. coli producing the extracellular bacterial amyloid protein curli. Rats exposed to curli-producing bacteria displayed increased neuronal AS deposition in both gut and brain and enhanced microgliosis and astrogliosis compared to rats exposed to either mutant bacteria unable to synthesize curli, or to vehicle alone. Animals exposed to curli producing bacteria also had more expression of TLR2, IL-6 and TNF in the brain than the other two groups. There were no differences among the rat groups in survival, body weight, inflammation in the mouth, retina, kidneys or gut epithelia, and circulating cytokine levels. AS-expressing C. elegans fed on curli-producing bacteria also had enhanced AS aggregation. These results suggest that bacterial amyloid functions as a trigger to initiate AS aggregation through cross-seeding and also primes responses of the innate immune system. PMID:27708338

  13. Feasibility of EPS-producing bacterial inoculation to speed up the sand aggregation in the Gurbantunggut Desert, Northwestern China.

    PubMed

    Wu, Nan; Pan, Hui-Xia; Qiu, Dong; Zhang, Yuan-Ming

    2014-12-01

    Exopolymers are known to be useful in improving sand aggregation and the development of biological soil crusts (BSCs). A facultative bacterium KLBB0001 was isolated from BSCs in the Gurbantunggut Desert in northwestern China. With the strong effective production of extracellular polymeric substances (EPS), this strain exhibits a multifunctional role for sand stabilization and maintenance of water under laboratory conditions. Practical testing of the feasibility of its inoculation to speed up BSC recovery in the field was also conducted in this experiment. This strain stimulated the heterotrophic community assembly in the topsoil layer (0-2 cm) before the commencement of autotrophic cyanobacteria, while also significantly increasing the number of bacteria, actinomycetes, and content of total phosphorus, available nitrogen, and available phosphorus. However, the low nitrogenase activity (NA) (0.57 µmol/h) that was observed caused us to doubt the previous identification as Azotobacter Beijerinck that was based on physiological and biochemical properties. A phylogenetic analysis based on 16S rRNA gene sequences revealed that this strain was a member of the genus Paenibacillus. It exhibited the closest phylogenetic affinity and highest sequence similarity to the strain Paenibacillus mucilaginosus VKPM B-7519 (sequence similarity 99.698%), which is well known as a typical silicate-weathering bacteria that releases lots of nutritional ions from minerals and the soil. Because P. mucilaginosus can excrete carbonic anhydrase (CA) to capture atmospheric CO2 through hydration of CO2 , it is possible that KLBB0001 might use a similar strategy for heterotrophs in the BSCs to sequester CO2 from the air. Because of its potential role in the reestablishment of the BSC ecosystem due to its ability to improve water relations, sand stabilization, and chemical erosion, EPS-producing bacterial inoculation was concluded to be a suitable and effective treatment for BSC recovery

  14. Modeling FtsZ ring formation in the bacterial cell—anisotropic aggregation via mutual interactions of polymer rods

    NASA Astrophysics Data System (ADS)

    Fischer-Friedrich, Elisabeth; Gov, Nir

    2011-04-01

    The cytoskeletal protein FtsZ polymerizes to a ring structure (Z ring) at the inner cytoplasmic membrane that marks the future division site and scaffolds the division machinery in many bacterial species. FtsZ is known to polymerize in the presence of GTP into single-stranded protofilaments. In vivo, FtsZ polymers become associated with the cytoplasmic membrane via interaction with the membrane-binding proteins FtsA and ZipA. The FtsZ ring structure is highly dynamic and undergoes constantly polymerization and depolymerization processes and exchange with the cytoplasmic pool. In this theoretical study, we consider a scenario of Z ring self-organization via self-enhanced attachment of FtsZ polymers due to end-to-end interactions and lateral interactions of FtsZ polymers on the membrane. With the assumption of exclusively circumferential polymer orientations, we derive coarse-grained equations for the dynamics of the pool of cytoplasmic and membrane-bound FtsZ. To capture stochastic effects expected in the system due to low particle numbers, we simulate our computational model using a Gillespie-type algorithm. We obtain ring- and arc-shaped aggregations of FtsZ polymers on the membrane as a function of monomer numbers in the cell. In particular, our model predicts the number of FtsZ rings forming in the cell as a function of cell geometry and FtsZ concentration. We also calculate the time of FtsZ ring localization to the midplane in the presence of Min oscillations. Finally, we demonstrate that the assumptions and results of our model are confirmed by 3D reconstructions of fluorescently-labeled FtsZ structures in E. coli that we obtained.

  15. Modeling of trihalomethane cometabolism in nitrifying biofilters.

    PubMed

    Wahman, David G; Katz, Lynn E; Speitel, Gerald E

    2007-01-01

    The computer program AQUASIM was used to model biofilter experiments seeded with Lake Austin, Texas mixed-culture nitrifiers. These biofilters degraded four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Apparent steady-state data from the biofilter experiments and supporting batch experiments were used to estimate kinetic parameters for TCM, DBCM and ammonia degradation. Subsequently, the model was verified against other experimental biofilter data. To allow for full-scale simulations, BDCM and TBM rate constants were estimated using data from batch kinetic studies. Finally, the model was used to simulate full-scale filter performance under different filter surface loading rates and THM speciation seen in practice. Overall, total THM removals ranged from 16% to 54% in these simulations with influent total THM concentrations of 75-82microg/L, which illustrates the potential of THM cometabolism to have a significant impact on treated water quality.

  16. Real-time monitoring of quorum sensing in 3D-printed bacterial aggregates using scanning electrochemical microscopy.

    PubMed

    Connell, Jodi L; Kim, Jiyeon; Shear, Jason B; Bard, Allen J; Whiteley, Marvin

    2014-12-23

    Microbes frequently live in nature as small, densely packed aggregates containing ∼10(1)-10(5) cells. These aggregates not only display distinct phenotypes, including resistance to antibiotics, but also, serve as building blocks for larger biofilm communities. Aggregates within these larger communities display nonrandom spatial organization, and recent evidence indicates that this spatial organization is critical for fitness. Studying single aggregates as well as spatially organized aggregates remains challenging because of the technical difficulties associated with manipulating small populations. Micro-3D printing is a lithographic technique capable of creating aggregates in situ by printing protein-based walls around individual cells or small populations. This 3D-printing strategy can organize bacteria in complex arrangements to investigate how spatial and environmental parameters influence social behaviors. Here, we combined micro-3D printing and scanning electrochemical microscopy (SECM) to probe quorum sensing (QS)-mediated communication in the bacterium Pseudomonas aeruginosa. Our results reveal that QS-dependent behaviors are observed within aggregates as small as 500 cells; however, aggregates larger than 2,000 bacteria are required to stimulate QS in neighboring aggregates positioned 8 μm away. These studies provide a powerful system to analyze the impact of spatial organization and aggregate size on microbial behaviors.

  17. Performance and Biofilm Activity of Nitrifying Biofilters Removing Trihalomethanes

    EPA Science Inventory

    Nitrifying biofilters seeded with three different mixed-culture sources degraded trichloromethane (TCM) and dibromochloromethane (DBCM). In addition, resuspended biofilm degraded TCM, bromododichloromethane (BDCM), DBCM, and tribromomethane (TBM) in backwash batch kinetic tests,...

  18. Monochloramine Cometabolism by Nitrifying Biofilm Relevant to Drinking Water

    EPA Science Inventory

    Recently, biological monochloramine removal (i.e., cometabolism) by a pure culture ammonia–oxidizing bacteria, Nitrosomonas europaea, and a nitrifying mixed–culture have been shown to increase monochloramine demand. Although important, these previous suspended culture batch kine...

  19. Performance and Biofilm Activity of Nitrifying Biofilters Removing Trihalomethanes

    EPA Science Inventory

    Nitrifying biofilters seeded with three different mixed-culture sources degraded trichloromethane (TCM) and dibromochloromethane (DBCM). In addition, resuspended biofilm degraded TCM, bromododichloromethane (BDCM), DBCM, and tribromomethane (TBM) in backwash batch kinetic tests,...

  20. Monochloramine Cometabolism by Nitrifying Biofilm Relevant to Drinking Water

    EPA Science Inventory

    Recently, biological monochloramine removal (i.e., cometabolism) by a pure culture ammonia–oxidizing bacteria, Nitrosomonas europaea, and a nitrifying mixed–culture have been shown to increase monochloramine demand. Although important, these previous suspended culture batch kine...

  1. A zeta potential value determines the aggregate's size of penta-substituted [60]fullerene derivatives in aqueous suspension whereas positive charge is required for toxicity against bacterial cells.

    PubMed

    Deryabin, Dmitry G; Efremova, Ludmila V; Vasilchenko, Alexey S; Saidakova, Evgeniya V; Sizova, Elena A; Troshin, Pavel A; Zhilenkov, Alexander V; Khakina, Ekaterina A; Khakina, Ekaterina E

    2015-08-08

    The cause-effect relationships between physicochemical properties of amphiphilic [60]fullerene derivatives and their toxicity against bacterial cells have not yet been clarified. In this study, we report how the differences in the chemical structure of organic addends in 10 originally synthesized penta-substituted [60]fullerene derivatives modulate their zeta potential and aggregate's size in salt-free and salt-added aqueous suspensions as well as how these physicochemical characteristics affect the bioenergetics of freshwater Escherichia coli and marine Photobacterium phosphoreum bacteria. Dynamic light scattering, laser Doppler micro-electrophoresis, agarose gel electrophoresis, atomic force microscopy, and bioluminescence inhibition assay were used to characterize the fullerene aggregation behavior in aqueous solution and their interaction with the bacterial cell surface, following zeta potential changes and toxic effects. Dynamic light scattering results indicated the formation of self-assembled [60]fullerene aggregates in aqueous suspensions. The measurement of the zeta potential of the particles revealed that they have different surface charges. The relationship between these physicochemical characteristics was presented as an exponential regression that correctly described the dependence of the aggregate's size of penta-substituted [60]fullerene derivatives in salt-free aqueous suspension from zeta potential value. The prevalence of DLVO-related effects was shown in salt-added aqueous suspension that decreased zeta potential values and affected the aggregation of [60]fullerene derivatives expressed differently for individual compounds. A bioluminescence inhibition assay demonstrated that the toxic effect of [60]fullerene derivatives against E. coli cells was strictly determined by their positive zeta potential charge value being weakened against P. phosphoreum cells in an aquatic system of high salinity. Atomic force microscopy data suggested that the

  2. Synthesis, aggregation and spectroscopic studies of novel water soluble metal free, zinc, copper and magnesium phthalocyanines and investigation of their anti-bacterial properties.

    PubMed

    Bayrak, Rıza; Akçay, Hakkı Türker; Beriş, Fatih Şaban; Sahin, Ertan; Bayrak, Hacer; Demirbaş, Ümit

    2014-12-10

    In this study, novel phthalonitrile derivative (3) was synthesized by the reaction between 4-nitrophthalonitrile (2) and a triazole derivative (1) containing pyridine moiety. Crystal structure of compound (3) was characterized by X-ray diffraction. New metal free and metallo-phthalocyanine complexes (Zn, Cu, and Mg) were synthesized using the phthalonitrile derivative (3). Cationic derivatives of these phthalocyanines (5, 7, 9, and 11) were prepared from the non-ionic phthalocyanines (4, 6, 8, and 10). All proposed structures were supported by instrumental methods. The aggregation behaviors of the phthalocyanines (4-11) were investigated in different solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), chloroform and water. Water soluble cationic Pcs (5, 7, 9, and 11) aggregated in water and sodium dodecyl sulfate was used to prevent the aggregation. The second derivatives of the UV-Vis spectra of aggregated Pcs were used for analyzing the Q and B bands of aggregated species. Thermal behaviors of the phthalocyanines were also studied. In addition, anti-bacterial properties of the phthalocyanines were investigated. We used four gram negative and two gram positive bacteria to determine antibacterial activity of these compounds. Compound 7 has the best activity against the all bacteria with 125μg/mL of MIC value. Compounds 4, 6, and 10 have the similar effect on the bacteria with 250μg/mL of MIC value.

  3. Synthesis, aggregation and spectroscopic studies of novel water soluble metal free, zinc, copper and magnesium phthalocyanines and investigation of their anti-bacterial properties

    NASA Astrophysics Data System (ADS)

    Bayrak, Rıza; Akçay, Hakkı Türker; Beriş, Fatih Şaban; Şahin, Ertan; Bayrak, Hacer; Demirbaş, Ümit

    2014-12-01

    In this study, novel phthalonitrile derivative (3) was synthesized by the reaction between 4-nitrophthalonitrile (2) and a triazole derivative (1) containing pyridine moiety. Crystal structure of compound (3) was characterized by X-ray diffraction. New metal free and metallo-phthalocyanine complexes (Zn, Cu, and Mg) were synthesized using the phthalonitrile derivative (3). Cationic derivatives of these phthalocyanines (5, 7, 9, and 11) were prepared from the non-ionic phthalocyanines (4, 6, 8, and 10). All proposed structures were supported by instrumental methods. The aggregation behaviors of the phthalocyanines (4-11) were investigated in different solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), chloroform and water. Water soluble cationic Pcs (5, 7, 9, and 11) aggregated in water and sodium dodecyl sulfate was used to prevent the aggregation. The second derivatives of the UV-Vis spectra of aggregated Pcs were used for analyzing the Q and B bands of aggregated species. Thermal behaviors of the phthalocyanines were also studied. In addition, anti-bacterial properties of the phthalocyanines were investigated. We used four gram negative and two gram positive bacteria to determine antibacterial activity of these compounds. Compound 7 has the best activity against the all bacteria with 125 μg/mL of MIC value. Compounds 4, 6, and 10 have the similar effect on the bacteria with 250 μg/mL of MIC value.

  4. In Situ Identification and Stratification of Monochloramine Inhibition Effects on Nitrifying Biofilms as Determined by the Use of Microelectrodes

    EPA Science Inventory

    The nitrifying biofilm grown in an annular biofilm reactor and the microbial deactivation achieved after monochloramine treatment were investigated using microelectrodes. The nitrifying biofilm ammonium microprofile was measured and the effect of monochloramine on nitrifying bio...

  5. In Situ Identification and Stratification of Monochloramine Inhibition Effects on Nitrifying Biofilms as Determined by the Use of Microelectrodes

    EPA Science Inventory

    The nitrifying biofilm grown in an annular biofilm reactor and the microbial deactivation achieved after monochloramine treatment were investigated using microelectrodes. The nitrifying biofilm ammonium microprofile was measured and the effect of monochloramine on nitrifying bio...

  6. Experimental manipulation of sponge/bacterial symbiont community composition with antibiotics: sponge cell aggregates as a unique tool to study animal/microorganism symbiosis.

    PubMed

    Richardson, Crystal; Hill, Malcolm; Marks, Carolyn; Runyen-Janecky, Laura; Hill, April

    2012-08-01

    Marine sponges can harbor dense and diverse bacterial communities, yet we have a limited understanding of important aspects of this symbiosis. We developed an experimental methodology that permits manipulating the composition of the microbial community. Specifically, we evaluated sponge cell aggregates (SCA) from Clathria prolifera that had been treated with different classes of antibiotics to determine whether this system might offer novel experimental approaches to the study of sponge/bacterial symbioses. Microscopic analysis of the SCA demonstrated that two distinct morphological types of microbiota existed on the external surface vs. the internal regions of the SCA. Denaturing gradient gel electrophoresis and sequence analysis of 16S rRNA gene clone libraries indicated that we were unable to create entirely aposymbiotic SCA but that different classes of antibiotics produced distinctive shifts in the SCA-associated bacterial community. After exposure to antibiotics, some bacterial species were 'revealed', thus uncovering novel components of the sponge-associated community. The antibiotic treatments used here had little discernible effect on the formation of SCA or subsequent development of the adult. The experimental approach we describe offers empirical options for studying the role symbionts play in sponge growth and development and for ascertaining relationships among bacterial species in communities residing in sponges.

  7. Monochloramine Cometabolism by Mixed-Culture Nitrifiers ...

    EPA Pesticide Factsheets

    The current research investigated monochloramine cometabolism by nitrifying mixed cultures grown under drinking water relevant conditions and harvested from sand-packed reactors before conducting suspended growth batch kinetic experiments. Three batch reactors were used in each experiment: (1) a positive control to estimate ammonia kinetic parameters, (2) a negative control to account for abiotic reactions, and (3) a cometabolism reactor to estimate cometabolism kinetic constants. Kinetic parameters were estimated in AQUASIM with a simultaneous fit to all experimental data. Cometabolism kinetics were best described by a first order model. Monochloramine cometabolism kinetics were similar to those of ammonia metabolism, and monochloramine cometabolism was a significant loss mechanism (30% of the observed monochloramine loss). These results demonstrated that monochloramine cometabolism occurred in mixed cultures similar to those found in drinking water distribution systems; thus, cometabolism may be a significant contribution to monochloramine loss during nitrification episodes in drinking water distribution systems. The results demonstrated that monochloramine cometabolism occurred in mixed cultures similar to those found in drinking water distribution systems; thus, cometabolism may be a significant contribution to monochloramine loss during nitrification episodes in drinking water distribution systems.

  8. Advanced nitrogen elimination by encapsulated nitrifiers.

    PubMed

    Sievers, M; Vorlop, K D; Hahne, J; Schlieker, M; Schäfer, S

    2003-01-01

    By introducing a mixed population of nitrifiers encapsulated in gel lens beads a more selective nitrification process was found in treatment of settled sewage in lab scale at a hydraulic retention time (HRT) of about 30 to 60 minutes. The reaction rates for oxidation of soluble chemical oxygen demand (SCOD) were found to vary between 25 to 150 mg/L x h while nitrification takes place around 50 mg nitrogen per hour and litre reaction volume. However, based on this SCOD removal in the nitrification step, a consequent post-denitrification process without nitrate recycle and dosage of external carbon sources has been proven to reach substantial nitrate elimination of up to 20 mg nitrogen per litre at COD/N-ratios of approx. 6 in settled sewage. At such COD/N-ratios, suitable nitrogen elimination seems to be possible, because the bioflocs of settled sewage, produced so far by SCOD oxidation and entrapment of particulate COD, are passing through the nitrification process having a substantial contribution to the denitrification rate additionally to the remaining SCOD.

  9. Enumeration and activity of nitrifying bacteria in zeoponic substrates

    NASA Astrophysics Data System (ADS)

    McGilloway, Robyn Leigh

    Regenerative life-support systems are needed for long-term space missions. One component of a proposed life-support system is the use of zeoponic growth substrates, which slowly release NH4 into 'soil' solution for the production of plants. Nitrifying bacteria that convert NH4 to NO3 are among the important microbial components of these systems. Some evidence suggests that a balance between NH4 and NO3 is desirable in promoting plant growth and seed development. Therefore, enumeration of nitrifying bacteria and evaluation of the kinetics of nitrification in zeoponic substrates warrants investigation. A method for rapid detection and enumeration of a commercial inoculum of nitrifying bacteria in a zeoponic substrate was developed using a most probable number (MPN)-polymerase chain reaction (PCR) approach, and a TaqMan probe-based assay. The detection limit of the MPN-PCR methodology was 2,000 cells per assay. Detection sensitivity for the TaqMan assay was determined to be 60 cells. The quantitative assay demonstrated that the zeoponic substrate was capable of supporting 105 to 107 Nitrobacter cells g-1 substrate. The MPN-PCR method and TaqMan probe-based assay can be effective and rapid approaches to enumerate nitrifying bacteria in zeoponic substrates. Column studies and a growth chamber study were conducted to evaluate the production of NO2 and NO3, and nitrifier populations in zeoponic substrates. The zeoponic substrate provided a readily available source of NH4, and nitrifying bacteria were active in the substrate. Quantities of NH4 oxidized, 10 mug N g-1 h-1, to NO2 and NO3 in inoculated zeoponic substrate were in excess of plant uptake. Acidification as a result of NH4 oxidation resulted in decline of pH to 5.5. The zeoponic substrate showed limited pH buffering capacity. Survival of nitrifying bacteria during periods of desiccation was evaluated, as the zeoponic substrate would likely be stored in an air-dry state between croppings. Substrate was enriched for

  10. Nitrification in histosols: a potential role for the heterotrophic nitrifier.

    PubMed Central

    Tate, R L

    1977-01-01

    Insufficient populations of Nitrosomonas and Nitrobacter were found in a Pahokee muck soil (Lithic medidaprit) to account for the nitrate concentration observed. To determine if heterotrophic nitrifiers could account for some of this discrepancy, a method was developed to measure the levels of heterotrophic nitrifiers in soil. A population of 4.1 X 10(5) Arthrobacter per g of dry fallow soil, capable of producing nitrite and/or nitrate from reduced nitrogenous compounds, was observed. Amendment of the much with 0.5% (wt/wt) sodium acetate and 0.1% (wt/wt) ammonium-nitrogen as ammonium sulfate (final concentrations) not only resulted in the usual increase in autotrophic nitrifiers, but also in a fourfold increase in the heterotrophic nitrifying Arrthrobacter. Amendment of like samples with N-Serve [2-chloro-6(trichloromethyl) pyridinel] prevented the increase in Nitrosomonas, but not that in the heterotrophic nitrifiers. Nitrate production in the presence of the inhibitor was diminished but not prevented. An Arthrobacter sp., isolated from the muck, produced nitrite when inoculated at high densities into sterile soil, unamended or amended with sodium acetate and/or ammomium sulfate. These data suggest that the heterotrophic population may be responsible for some of the nitrate produced in these Histosols. PMID:869537

  11. Population of Nitrifying Bacteria and Nitrification in Ammonium Saturated Clinoptilolite

    NASA Technical Reports Server (NTRS)

    McGilloway, R. L.; Weaver, R. W.; Ming, Douglas W.; Gruener, J.

    1999-01-01

    As humans begin to spend longer periods of time in space, plants will be incorporated into life support systems. Ammonium saturated clinoptilolite is one plant growth substrate but a balance between ammonium and nitrate is needed. A laboratory study was conducted to determine effects of nitrifying bacteria on ammonium concentrations and kinetics of nitrification. Columns containing clinoptilolite substrate amended with nitrifying bacteria obtained from soil enrichment were analyzed weekly for a 90 day period. The enrichment culture initially contained 1 x 10(exp 5) ammonium oxidizing bacteria and 1 x 10(exp 2) nitrite oxidizing bacteria per gram of substrate. Populations of ammonium oxidizing bacteria increased to 1 x 10(exp 6) and nitrite oxidizing bacteria increased to 1 x 10(exp 3) per gram of substrate. The nitrification rate was approximately 0.25mg NO3(-)-N/kg.hr. Experiments were also conducted to enumerate nitrifying bacteria in a clinoptilolite substrate used to grow wheat (Triticum aestivum L.). Seventy days following the initial inoculation with an unknown number of commercial nitrifying bacteria, 1 x 10(exp 5) ammonium oxidizing bacteria per gram of substrate were present. The number of nitrite oxidizing bacteria was between 1 x 10(exp 3) to 10(exp 4) per gram of substrate as measured by the most probable number method. Nitrification rates were approximately 0.20mg NO3(-)-N/kg.hr. Clinoptilolite readily exchanged sufficient concentrations of ammonium to support nitrifying bacteria and they survived well in this medium.

  12. Population of Nitrifying Bacteria and Nitrification in Ammonium Saturated Clinoptilolite

    NASA Technical Reports Server (NTRS)

    McGilloway, R. L.; Weaver, R. W.; Ming, Douglas W.; Gruener, J.

    1999-01-01

    As humans begin to spend longer periods of time in space, plants will be incorporated into life support systems. Ammonium saturated clinoptilolite is one plant growth substrate but a balance between ammonium and nitrate is needed. A laboratory study was conducted to determine effects of nitrifying bacteria on ammonium concentrations and kinetics of nitrification. Columns containing clinoptilolite substrate amended with nitrifying bacteria obtained from soil enrichment were analyzed weekly for a 90 day period. The enrichment culture initially contained 1 x 10(exp 5) ammonium oxidizing bacteria and 1 x 10(exp 2) nitrite oxidizing bacteria per gram of substrate. Populations of ammonium oxidizing bacteria increased to 1 x 10(exp 6) and nitrite oxidizing bacteria increased to 1 x 10(exp 3) per gram of substrate. The nitrification rate was approximately 0.25mg NO3(-)-N/kg.hr. Experiments were also conducted to enumerate nitrifying bacteria in a clinoptilolite substrate used to grow wheat (Triticum aestivum L.). Seventy days following the initial inoculation with an unknown number of commercial nitrifying bacteria, 1 x 10(exp 5) ammonium oxidizing bacteria per gram of substrate were present. The number of nitrite oxidizing bacteria was between 1 x 10(exp 3) to 10(exp 4) per gram of substrate as measured by the most probable number method. Nitrification rates were approximately 0.20mg NO3(-)-N/kg.hr. Clinoptilolite readily exchanged sufficient concentrations of ammonium to support nitrifying bacteria and they survived well in this medium.

  13. Morphometric Evaluation of Interrenal Gland and Kidney Macrophages Aggregates in Normal Healthy Rainbow Trout (Oncorhynchus mykiss) and after Bacterial Challenge with Yersinia ruckeri.

    PubMed

    Gregori, Michela; Miragliotta, Vincenzo; Leotta, Roberto; Cecchini, Stefano; Prearo, Marino; Abramo, Francesca

    2014-01-01

    Macrophage aggregates (MA) occur in various organs of fish as discrete aggregations of pigmented macrophages. The study presented herein investigates the quantitative modifications from normal anatomical condition, of interrenal gland (IG) and kidney MA in six treatment groups of adult rainbow trout submitted to either specific or aspecific immune stimulation and subsequently challenged with Yersinia ruckeri. Routinely stained tissue sections from both IG and kidney were analysed. The percentage of tissues occupied by MA and the MA density (number/mm(2)) were calculated on at least 10 randomly selected nonoverlapping fields taken from each tissue section. MA morphometric findings from challenged fish were compared to those from a control group. Results showed that fish from control group displayed a statistically significant (P < 0.05) higher percentage of tissue occupied by MA and MA density. Among different treatment groups, anti-Yersinia ruckeri immunized fish, which did not show clinical signs of disease after bacterial challenge, displayed higher values of morphometric parameters compared with symptomatic fish from other groups. Our study demonstrates that the quantification of the area occupied by MA might be an efficient parameter to evaluate the general condition of a salmonid population since it positively correlates with the health status and negatively with stress factor such as the acute bacterial infection.

  14. Morphometric Evaluation of Interrenal Gland and Kidney Macrophages Aggregates in Normal Healthy Rainbow Trout (Oncorhynchus mykiss) and after Bacterial Challenge with Yersinia ruckeri

    PubMed Central

    Gregori, Michela; Miragliotta, Vincenzo; Leotta, Roberto; Cecchini, Stefano; Prearo, Marino; Abramo, Francesca

    2014-01-01

    Macrophage aggregates (MA) occur in various organs of fish as discrete aggregations of pigmented macrophages. The study presented herein investigates the quantitative modifications from normal anatomical condition, of interrenal gland (IG) and kidney MA in six treatment groups of adult rainbow trout submitted to either specific or aspecific immune stimulation and subsequently challenged with Yersinia ruckeri. Routinely stained tissue sections from both IG and kidney were analysed. The percentage of tissues occupied by MA and the MA density (number/mm2) were calculated on at least 10 randomly selected nonoverlapping fields taken from each tissue section. MA morphometric findings from challenged fish were compared to those from a control group. Results showed that fish from control group displayed a statistically significant (P < 0.05) higher percentage of tissue occupied by MA and MA density. Among different treatment groups, anti-Yersinia ruckeri immunized fish, which did not show clinical signs of disease after bacterial challenge, displayed higher values of morphometric parameters compared with symptomatic fish from other groups. Our study demonstrates that the quantification of the area occupied by MA might be an efficient parameter to evaluate the general condition of a salmonid population since it positively correlates with the health status and negatively with stress factor such as the acute bacterial infection. PMID:24719776

  15. Metabolic strategies of free-living and aggregate-associated bacterial communities inferred from biologic and chemical profiles in the Black Sea suboxic zone.

    PubMed

    Fuchsman, Clara A; Kirkpatrick, John B; Brazelton, William J; Murray, James W; Staley, James T

    2011-12-01

    The Black Sea is a permanently anoxic basin with a well-defined redox gradient. We combine environmental 16S rRNA gene data from clone libraries, terminal restriction fragment length polymorphisms, and V6 hypervariable region pyrosequences to provide the most detailed bacterial survey to date. Furthermore, this data set is informed by comprehensive geochemical data; using this combination of information, we put forward testable hypotheses regarding possible metabolisms of uncultured bacteria from the Black Sea's suboxic zone (microaerophily, nitrate reduction, manganese cycling, and oxidation of methane, ammonium, and sulfide). Dominant bacteria in the upper suboxic zone included members of the SAR11, SAR324, and Microthrix groups and in the deep suboxic zone included members of BS-GSO-2, Marine Group A, and SUP05. A particulate fraction (30 μm filter) was used to distinguish between free-living and aggregate-attached communities in the suboxic zone. The particulate fraction contained greater diversity of V6 tag sequences than the bulk water samples. Lentisphaera, Epsilonproteobacteria, WS3, Planctomycetes, and Deltaproteobacteria were enriched in the particulate fraction, whereas SAR11 relatives dominated the free-living fraction. On the basis of the bacterial assemblages and simple modeling, we find that in suboxic waters, the interior of sinking aggregates potentially support manganese reduction, sulfate reduction, and sulfur oxidation.

  16. Responses of the Microalga Chlorophyta sp. to Bacterial Quorum Sensing Molecules (N-Acylhomoserine Lactones): Aromatic Protein-Induced Self-Aggregation.

    PubMed

    Zhou, Dandan; Zhang, Chaofan; Fu, Liang; Xu, Liang; Cui, Xiaochun; Li, Qingcheng; Crittenden, John C

    2017-03-21

    Bacteria and microalgae often coexist during the recycling of microalgal bioresources in wastewater treatment processes. Although the bacteria may compete with the microalgae for nutrients, they could also facilitate microalgal harvesting by forming algal-bacterial aggregates. However, very little is known about interspecies interactions between bacteria and microalgae. In this study, we investigated the responses of a model microalga, Chlorophyta sp., to the typical quorum sensing (QS) molecules N-acylhomoserine lactones (AHLs) extracted from activated sludge bacteria. Chlorophyta sp. self-aggregated in 200 μm bioflocs by secreting 460-1000 kDa aromatic proteins upon interacting with AHLs, and the settling efficiency of Chlorophyta sp. reached as high as 41%. However, Chlorophyta sp. cells were essentially in a free suspension in the absence of AHLs. Fluorescence intensity of the aromatic proteins had significant (P < 0.05) relationship with the Chlorophyta sp. settleability, and showed a positive correlation, indicating that aromatic proteins helped aggregate microalga. Transcriptome results further revealed up-regulation of synthesis pathways for aromatic proteins from tyrosine and phenylalanine that was assisted by anthranilate accumulation. To the best of our knowledge, this is the first study to confirm that eukaryotic microorganisms can sense and respond to prokaryotic QS molecules.

  17. Thioflavin-S staining of bacterial inclusion bodies for the fast, simple, and inexpensive screening of amyloid aggregation inhibitors.

    PubMed

    Pouplana, S; Espargaro, A; Galdeano, C; Viayna, E; Sola, I; Ventura, S; Muñoz-Torrero, D; Sabate, R

    2014-01-01

    Amyloid aggregation is linked to a large number of human disorders, from neurodegenerative diseases as Alzheimer's disease (AD) or spongiform encephalopathies to non-neuropathic localized diseases as type II diabetes and cataracts. Because the formation of insoluble inclusion bodies (IBs) during recombinant protein production in bacteria has been recently shown to share mechanistic features with amyloid self-assembly, bacteria have emerged as a tool to study amyloid aggregation. Herein we present a fast, simple, inexpensive and quantitative method for the screening of potential anti-aggregating drugs. This method is based on monitoring the changes in the binding of thioflavin-S to intracellular IBs in intact Eschericchia coli cells in the presence of small chemical compounds. This in vivo technique fairly recapitulates previous in vitro data. Here we mainly use the Alzheimer's related β-amyloid peptide as a model system, but the technique can be easily implemented for screening inhibitors relevant for other conformational diseases simply by changing the recombinant amyloid protein target. Indeed, we show that this methodology can be also applied to the evaluation of inhibitors of the aggregation of tau protein, another amyloidogenic protein with a key role in AD.

  18. Aggregation-Induced-Emission Materials with Different Electric Charges as an Artificial Tongue: Design, Construction, and Assembly with Various Pathogenic Bacteria for Effective Bacterial Imaging and Discrimination.

    PubMed

    Liu, Guang-Jian; Tian, Sheng-Nan; Li, Cui-Yun; Xing, Guo-Wen; Zhou, Lei

    2017-08-30

    Imaging-based total bacterial count and type identification of bacteria play crucial roles in clinical diagnostics, public health, biological and medical science, and environmental protection. Herein, we designed and synthesized a series of tetraphenylethenes (TPEs) functionalized with one or two aldehyde, carboxylic acid, and quaternary ammonium groups, which were successfully used as fluorescent materials for rapid and efficient staining of eight kinds of representative bacterial species, including pathogenic bacteria Vibrio cholera, Klebsiella pneumoniae, and Listeria monocytogenes and potential bioterrorism agent Yersinia pestis. By comparing the fluorescence intensity changes of the aggregation-induced-emission (AIE) materials before and after bacteria incubation, the sensing mechanisms (electrostatic versus hydrophobic interactions) were simply discussed. Moreover, the designed AIE materials were successfully used as an efficient artificial tongue for bacteria discrimination, and all of the bacteria tested were identified via linear discriminant analysis. Our current work provided a general method for simultaneous broad-spectrum bacterial imaging and species discrimination, which is helpful for bacteria surveillance in many fields.

  19. 2-Chlorophenol consumption and its effect on the nitrifying sludge.

    PubMed

    Martínez-Hernández, Sergio; Texier, Anne-Claire; de María Cuervo-López, Flor; Gómez, Jorge

    2011-01-30

    The kinetic behavior of a nitrifying sludge exposed to 2-chlorophenol (2-CP) was evaluated in batch culture. The assays were performed using a stabilized nitrifying sludge. In control assays with (mg L(-1)): NH(4)(+)-N (100) and NaHCO(3)(-)-C (250), the substrates were consumed in 8h, the ammonium consumption efficiency was 99% and the NO(3)(-) yield higher than 0.9. When 5mg 2-CP-C L(-1) was added, it was transformed into an unidentified intermediate and the nitrifying efficiency decreased to 10%. Ammonium specific consumption rate diminished 95%, but the NO(3)(-) yield remained higher than 0.9. The biomass previously exposed to 2-CP was newly suspended with NH(4)(+)-N or NO(2)(-)-N in order to evaluate the ammonium and nitrite oxidizing processes. The consumption efficiencies and NO(3)(-) yields were similar to those obtained in control assays. However, the total time required for ammonium and nitrite consumption increased to 120 and 42 h, respectively. Specific consumption rates for NH(4)(+)-N and NO(2)(-)-N decreased by 95% and 83% respectively, compared to control assays. Thus, the previous contact to 2-CP had more influence on ammonium oxidizing process than the nitrite oxidizing process. These are the first evidences where a nitrifying sludge exposed to 2-CP are reported. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. A Spectroscopic Study of the Aggregation State of the Human Antimicrobial Peptide LL-37 in Bacterial versus Host Cell Model Membranes.

    PubMed

    Bonucci, Alessio; Caldaroni, Elena; Balducci, Enrico; Pogni, Rebecca

    2015-11-17

    The LL-37 antimicrobial peptide is the only cathelicidin peptide found in humans that has antimicrobial and immunomodulatory properties. Because it exerts also chemotactic and angiogenetic activity, LL-37 is involved in promoting wound healing, reducing inflammation, and strengthening the host immune response. The key to the effectiveness of antimicrobial peptides (AMPs) lies in the different compositions of bacterial versus host cell membranes. In this context, antimicrobial peptide LL-37 and two variants were studied in the presence of model membranes with different lipid compositions and charges. The investigation was performed using an experimental strategy that combines the site-directed spin labeling-electron paramagnetic resonance technique with circular dichroism and fluorescence emission spectroscopies. LL-37 interacts with negatively charged membranes forming a stable aggregate, which can likely produce toroidal pores until the amount of bound peptide exceeds a critical concentration. At the same time, we have clearly detected an aggregate with a higher oligomeric degree for interaction of LL-37 with neutral membranes. These data confirm the absence of cell selectivity of the peptide and a more complex role in stimulating host cells.

  1. Silk macromolecules with amino acid-poly(ethylene glycol) grafts for controlling layer-by-layer encapsulation and aggregation of recombinant bacterial cells.

    PubMed

    Drachuk, Irina; Calabrese, Rossella; Harbaugh, Svetlana; Kelley-Loughnane, Nancy; Kaplan, David L; Stone, Morley; Tsukruk, Vladimir V

    2015-02-24

    This study introduces double-brush designs of functionalized silk polyelectrolytes based upon regenerated silk fibroin (SF), which is modified with poly-L-lysine (SF-PLL), poly-L-glutamic acid (SF-PGA), and poly(ethylene glycol) (PEG) side chains with different grafting architecture and variable amino acid-PEG graft composition for cell encapsulation. The molecular weight of poly amino acids (length of side chains), molecular weight and degree of PEG grafting (D) were varied in order to assess the formation of cytocompatible and robust layer-by-layer (LbL) shells on two types of bacterial cells (Gram-negative and Gram-positive bacteria). We observed that shells assembled with charged polycationic amino acids adversely effected the properties of microbial cells while promoting the formation of large cell aggregates. In contrast, hydrogen-bonded shells with high PEG grafting density were the most cytocompatible, while promoting formation of stable colloidal suspensions of individual cell encapsulates. The stability to degradation of silk shells (under standard cell incubation procedure) was related to the intrinsic properties of thermodynamic bonding forces, with shells based on electrostatic interactions having stronger resistance to deterioration compared to pure hydrogen-bonded silk shells. By optimizing the charge density of silk polyelectrolytes brushes, as well as the length and the degree of PEG side grafts, robust and cytocompatible cell coatings were engineered that can control aggregation of cells for biosensor devices and other potential biomedical applications.

  2. Effect of different mixing methods on the bacterial microleakage of white Portland cement and white Mineral Trioxide Aggregate

    PubMed Central

    Shahi, Shahriar; Bashirzadeh, Asmar; Yavari, Hamid Reza; Jafari, Farnaz; Salem Milani, Amin; Ghasemi, Negin; Samiei, Mohammad

    2017-01-01

    Background. of this study was to investigate the effect of different mixing methods (ultrasonic, amalgamator, and conventional) on the bacterial microleakage of white Portland cement (WPC) and white MTA (Tooth-colored Formula, Dentsply, Tulsa Dental, Tulsa, OK). Methods. A hundred human single-rooted permanent teeth were decoronated to obtain 14 mm of root length in all the samples. The root canals were cleaned, shaped and obturated. Three millimeters of each root apex were cut off and randomly divided into 6 groups of 15 each (3 groups for WMTA and 3 groups for WPC, each with 3 different mixing methods) and 2 positive and negative control groups (each containing 5 samples). Brain-heart infusion agar (BHI) suspension containing the bacterial species Enterococcus faecalis (ATCC 29212) was used for leakage assessment. Statistical analysis was carried out using descriptive statistics and Kaplan Mayer survival analysis with censored data and log rank test using SPSS 18. Statistical significance was set at P<0.05. Results. The survival means in PC for conventional method, amalgamator, and ultrasonic were 80.2±13.64, 78.5±13.46 and 84.667±11.42 days, with 49.13±12.96, 66±13.32 and 69.07±11.5 days for MTA, respectively. The log rank test showed no significant differences between the three methods in each material (P>0.05). Conclusion. Bacterial microleakage in the studied samples was not significantly different in terms of the type of the mixing method. PMID:28748048

  3. Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge.

    PubMed

    Forget, Nathalie L; Kim Juniper, S

    2013-04-01

    We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus-Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. © 2013 The Authors. Published by Blackwell Publishing Ltd.

  4. Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge

    PubMed Central

    Forget, Nathalie L; Kim Juniper, S

    2013-01-01

    We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus–Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. PMID:23401293

  5. Microbial community response of nitrifying sequencing batch reactors to silver, zero-valent iron, titanium dioxide and cerium dioxide nanomaterials.

    PubMed

    Ma, Yanjun; Metch, Jacob W; Vejerano, Eric P; Miller, Ian J; Leon, Elena C; Marr, Linsey C; Vikesland, Peter J; Pruden, Amy

    2015-01-01

    As nanomaterials in consumer products increasingly enter wastewater treatment plants, there is concern that they may have adverse effects on biological wastewater treatment. Effects of silver (nanoAg), zero-valent iron (NZVI), titanium dioxide (nanoTiO₂) and cerium dioxide (nanoCeO₂) nanomaterials on nitrification and microbial community structure were examined in duplicate lab-scale nitrifying sequencing batch reactors (SBRs) relative to control SBRs that received no nanomaterials or ionic/bulk analogs. Nitrification function was not measurably inhibited in the SBRs by any of the materials as dosing was initiated at 0.1 mg/L and sequentially increased every 14 days to 1, 10, and 20 mg/L. However, SBRs rapidly lost nitrification function when the Ag⁺ experiment was repeated at a continuous high load of 20 mg/L. Shifts in microbial community structure and decreased microbial diversity were associated with both sequential and high loading of nanoAg and Ag⁺, with more pronounced effects for Ag⁺. Bacteroidetes became more dominant in SBRs dosed with Ag⁺, while Proteobacteria became more dominant in SBRs dosed with nanoAg. The two forms of silver also had distinct effects on specific bacterial genera. A decrease in nitrification gene markers (amoA) was observed in SBRs dosed with nanoAg and Ag⁺. In contrast, impacts of NZVI, nanoTiO₂, nanoCeO₂ and their analogs on microbial community structure and nitrification gene markers were limited. TEM-EDS analysis indicated that a large portion of nanoAg remained dispersed in the activated sludge and formed Ag–S complexes, while NZVI, nanoTiO₂ and nanoCeO₂ were mostly aggregated and chemically unmodified. Overall, this study suggests a high threshold of the four nanomaterials in terms of exerting adverse effects on nitrification function. However, distinct microbial community responses to nanoAg indicate potential long-term effects.

  6. Carbon and Energy Sources for the Nitrifying Autotroph Nitrobacter

    PubMed Central

    Delwiche, C. C.; Finstein, M. S.

    1965-01-01

    Delwiche, C. C. (University of California, Davis), and M. S. Finstein. Carbon and energy sources for the nitrifying autotroph Nitrobacter. J. Bacteriol. 90:102–107. 1965.—The effect of various organic compounds on the growth and metabolism of the obligatively autotrophic nitrifying organism Nitrobacter was studied. A slight stimulation of both nitrification and growth was obtainable with a number of organic amendments, including yeast extract, Vitamin Free Casamino Acids, and some amino acids. Depending upon culture conditions, a strong stimulation of growth was obtained with acetate as an amendment to the culture solution. Several compounds, including valine, hydroxyproline, and threonine, were inhibitory at concentrations of 10−3m. The incorporation of carbon from isotopically labeled organic compounds was demonstrated. Acetate and glycine were particularly strong contributors to cell carbons. These could not substitute for carbon dioxide as a sole carbon source for growth, however, nor could any other of the carbon compounds that were tried. PMID:16562002

  7. Contamination of tooth-colored mineral trioxide aggregate used as a root-end filling material: a bacterial leakage study.

    PubMed

    Montellano, Angela M; Schwartz, Scott A; Beeson, Thomas J

    2006-05-01

    This experiment investigated the ability of tooth-colored mineral trioxide aggregate (MTA) to maintain an apical seal in the presence of bacteria when contaminated with blood, saline or saliva. Ninety extracted human teeth with single canals were randomly placed into six groups of 15. Canals were prepared to size 50. The apical 3 mm of each root was removed and 3 mm root-end preparations were made with a #329 bur. Root-end preparations in groups 1 through 3 were filled with MTA after contamination with blood, saline, or saliva, respectively. In group 4, uncontaminated root-end preparations were filled with MTA. Groups 5 and 6 served as negative and positive controls. A tube/tooth assembly was utilized to suspend each root end in Trypticase Soy Broth (TSB). The access chambers were filled with Staphylococcus epidermidis. Positive growth over thirty days was demonstrated by turbidity of the TSB. Vitek analysis was used to confirm the presence of S. epidermidis in the positive samples. Data evaluation consisted of a chi(2) analysis (p < 0.05). Although all experimental groups demonstrated leakage, tooth-colored MTA contaminated with saliva (group 3) leaked significantly more than the uncontaminated tooth-colored MTA (group 4) (p = 0.028).

  8. Tracking the dynamics of heterotrophs and nitrifiers in moving-bed biofilm reactors operated at different COD/N ratios.

    PubMed

    Bassin, J P; Abbas, B; Vilela, C L S; Kleerebezem, R; Muyzer, G; Rosado, A S; van Loosdrecht, M C M; Dezotti, M

    2015-09-01

    In this study, the impact of COD/N ratio and feeding regime on the dynamics of heterotrophs and nitrifiers in moving-bed biofilm reactors was addressed. Based on DGGE analysis of 16S rRNA genes, the influent COD was found to be the main factor determining the overall bacterial diversity. The amoA-gene-based analysis suggested that the dynamic behavior of the substrate in continuous and pulse-feeding reactors influenced the selection of specific ammonium-oxidizing bacteria (AOB) strains. Furthermore, AOB diversity was directly related to the applied COD/N ratio and ammonium-nitrogen load. Maximum specific ammonium oxidation rates observed under non-substrate-limiting conditions were observed to be proportional to the fraction of nitrifiers within the bacterial community. FISH analysis revealed that Nitrosomonas genus dominated the AOB community in all reactors. Moreover, Nitrospira was found to be the only nitrite-oxidizing bacteria (NOB) in the fully autotrophic system, whereas Nitrobacter represented the dominant NOB genus in the organic carbon-fed reactors.

  9. p-Cresol biotransformation by a nitrifying consortium.

    PubMed

    Silva, C D; Gómez, J; Houbron, E; Cuervo-López, F M; Texier, A-C

    2009-06-01

    The oxidizing ability of a nitrifying consortium exposed to p-cresol (25 mg CL(-1)) was evaluated in batch cultures. Biotransformation of the phenolic compound was investigated by identifying the different intermediates formed. p-Cresol inhibited the ammonia-oxidizing process with a decrease of 83% in the specific rate of ammonium consumption. After 48 h, ammonium consumption efficiency was 96+/-9% while nitrate yield reached 0.95+/-0.06 g NO(3)(-)-Ng(-1)NH(4)(+)-N consumed. High value for nitrate production yield showed that the nitrifying metabolic pathway was only affected at the specific rate level being nitrate the main end product. The consortium was able to totally oxidize p-cresol at a specific rate of 0.17+/-0.06 mg p-cresol-Cmg(-1) microbial protein h(-1). p-Cresol was first transformed to p-hydroxybenzaldehyde and p-hydroxybenzoate, which were later completely mineralized. In the presence of allylthiourea, a specific inhibitor of ammonia monooxygenase (AMO), p-cresol was oxidized to the same intermediates and in a similar pattern as obtained without the AMO inhibitor. AMO seemed not to be involved in the p-cresol oxidation process. When p-hydroxybenzaldehyde was added (25 mg CL(-1)), the nitrifying process was inhibited in the same way as observed with p-cresol, indicating that p-hydroxybenzaldehyde could be the main compound responsible for nitrification inhibition. p-Hydroxybenzaldehyde was accumulated during 15 h before complete consumption at a specific rate value eight times lower than the p-cresol consumption rate. Results showed that p-hydroxybenzaldehyde oxidation was the limiting step in p-cresol mineralization by the nitrifying consortium.

  10. Biotransformation of chlorinated aliphatic compounds by mixed nitrifying cultures

    SciTech Connect

    Wilber, G.G.; Chakkamadathil, S.V.

    1995-12-31

    The ability of pure cultures of nitrifying bacteria, such as Nitrosomonas europaea, to oxidize chlorinated aliphatic compounds has been demonstrated previously in laboratory experiments. In the current study, mixed nitrifying cultures originating from a municipal wastewater plant were also tested for the ability to biotransform chlorinated aliphatic compounds, including trichloroethene (TCE). A number of variables were tested, including the effects of two different concentrations of TCE, the effect of culture density, and the influence of the primary substrate, ammonia, on the initial rate of TCE biotransformation. The primary conclusions of the research include the following. The mixed nitrifying cultures did exhibit the ability to transform TCE, and the initial rate of transformation (before oxygen limitations became significant) was directly proportional to the culture density. In general, the transformation rate of TCE was slightly faster at an initial concentration of 0.1 mg/L than at 1 mg/L. Lastly, high initial ammonia concentrations (300 mg/L) resulted in faster initial rates of TCE transformation than in cultures which started with lower ammonia concentrations.

  11. Resistance of nitrifiers inhabiting activated sludge to ciliate grazing.

    PubMed

    Pajdak-Stós, Agnieszka; Fiałkowska, Edyta; Fyda, Janusz; Babko, Roman

    2010-01-01

    We monitored the succession of nitrifiers in a newly opened wastewater treatment plant for five weeks. After the first distinct decrease in total nitrogen, we began monitoring the appearance, size and number of nitrifying bacteria colonies using the fluorescence in situ hybridization (FISH) method. Ammonia oxidizing bacteria (AOB) colonies were visualized under green excitation as red, and nitrite oxidizing bacteria (NOB) colonies were visualized under blue excitation as green. The changes in protozoan community were monitored simultaneously. Ciliates were divided into four functional groups: predatory, bacterivorous free-swimming, bacterivorous crawling, and sessile. The results showed that at the time of the first distinct total nitrogen decrease, the mean length of both AOB and NOB were relatively low, but the colonies, especially those of nitrite oxidizers, were abundant. In time, the distribution of ammonia oxidizer colonies shifted towards larger sizes, but their quantity decreased. In the case of nitrite oxidizers, a similar trend was noticeable but less pronounced. These changes corresponded with an increasing number of crawling bacterivorous ciliates dominated by the "scavenger" genus Aspidisca. The increasing size of nitrifier colonies may have been due to the growing grazing pressure from crawling bacterivorous ciliates. The strong grazing pressure did not negatively affect N-NH(4)(+) removal effectiveness.

  12. Low-Dissolved-Oxygen Nitrifying Systems Exploit Ammonia-Oxidizing Bacteria with Unusually High Yields▿

    PubMed Central

    Bellucci, Micol; Ofiţeru, Irina D.; Graham, David W.; Head, Ian M.; Curtis, Thomas P.

    2011-01-01

    In wastewater treatment plants, nitrifying systems are usually operated with elevated levels of aeration to avoid nitrification failures. This approach contributes significantly to operational costs and the carbon footprint of nitrifying wastewater treatment processes. In this study, we tested the effect of aeration rate on nitrification by correlating ammonia oxidation rates with the structure of the ammonia-oxidizing bacterial (AOB) community and AOB abundance in four parallel continuous-flow reactors operated for 43 days. Two of the reactors were supplied with a constant airflow rate of 0.1 liter/min, while in the other two units the airflow rate was fixed at 4 liters/min. Complete nitrification was achieved in all configurations, though the dissolved oxygen (DO) concentration was only 0.5 ± 0.3 mg/liter in the low-aeration units. The data suggest that efficient performance in the low-DO units resulted from elevated AOB levels in the reactors and/or putative development of a mixotrophic AOB community. Denaturing gel electrophoresis and cloning of AOB 16S rRNA gene fragments followed by sequencing revealed that the AOB community in the low-DO systems was a subset of the community in the high-DO systems. However, in both configurations the dominant species belonged to the Nitrosomonas oligotropha lineage. Overall, the results demonstrated that complete nitrification can be achieved at low aeration in lab-scale reactors. If these findings could be extended to full-scale plants, it would be possible to minimize the operational costs and greenhouse gas emissions without risk of nitrification failure. PMID:21926211

  13. Kinetics of bacterial phospholipase C activity at micellar interfaces: effect of substrate aggregate microstructure and a model for the kinetic parameters.

    PubMed

    Singh, Jasmeet; Ranganathan, Radha; Hajdu, Joseph

    2008-12-25

    Activity at micellar interfaces of bacterial phospholipase C from Bacillus cereus on phospholipids solubilized in micelles was investigated with the goal of elucidating the role of the interface microstructure and developing further an existing kinetic model. Enzyme kinetics and physicochemical characterization of model substrate aggregates were combined, thus enabling the interpretation of kinetics in the context of the interface. Substrates were diacylphosphatidylcholine of different acyl chain lengths in the form of mixed micelles with dodecyldimethylammoniopropanesulfonate. An early kinetic model, reformulated to reflect the interfacial nature of the kinetics, was applied to the kinetic data. A better method of data treatment is proposed, use of which makes the presence of microstructure effects quite transparent. Models for enzyme-micelle binding and enzyme-lipid binding are developed, and expressions incorporating the microstructural properties are derived for the enzyme-micelle dissociation constant K(s) and the interface Michaelis-Menten constant, K(M). Use of these expressions in the interface kinetic model brings excellent agreement between the kinetic data and the model. Numerical values for the thermodynamic and kinetic parameters are determined. Enzyme-lipid binding is found to be an activated process with an acyl chain length dependent free energy of activation that decreases with micelle lipid molar fraction with a coefficient of about -15RT and correlates with the tightness of molecular packing in the substrate aggregate. Thus, the physical insight obtained includes a model for the kinetic parameters that shows that these parameters depend on the substrate concentration and acyl chain length of the lipid. Enzyme-micelle binding is indicated to be hydrophobic and solvent mediated with a dissociation constant of 1.2 mM.

  14. Population dynamics and in situ kinetics of nitrifying bacteria in autotrophic nitrifying biofilms as determined by real-time quantitative PCR.

    PubMed

    Kindaichi, Tomonori; Kawano, Yoshiko; Ito, Tsukasa; Satoh, Hisashi; Okabe, Satoshi

    2006-08-20

    Population dynamics of ammonia-oxidizing bacteria (AOB) and uncultured Nitrospira-like nitrite-oxidizing bacteria (NOB) dominated in autotrophic nitrifying biofilms were determined by using real-time quantitative polymerase chain reaction (RTQ-PCR) and fluorescence in situ hybridization (FISH). Although two quantitative techniques gave the comparable results, the RTQ-PCR assay was easier and faster than the FISH technique for quantification of both nitrifying bacteria in dense microcolony-forming nitrifying biofilms. Using this RTQ-PCR assay, we could successfully determine the maximum specific growth rate (mu = 0.021/h) of uncultured Nitrospira-like NOB in the suspended enrichment culture. The population dynamics of nitrifying bacteria in the biofilm revealed that once they formed the biofilm, the both nitrifying bacteria grew slower than in planktonic cultures. We also calculated the spatial distributions of average specific growth rates of both nitrifying bacteria in the biofilm based on the concentration profiles of NH4+, NO2-, and O2, which were determined by microelectrodes, and the double-Monod model. This simple model estimation could explain the stratified spatial distribution of AOB and Nitrospira-like NOB in the biofilm. The combination of culture-independent molecular techniques and microelectrode measurements is a very powerful approach to analyze the in situ kinetics and ecophysiology of nitrifying bacteria including uncultured Nitrospira-like NOB in complex biofilm communities.

  15. Employing bacterial microcompartment technology to engineer a shell-free enzyme-aggregate for enhanced 1,2-propanediol production in Escherichia coli.

    PubMed

    Lee, Matthew J; Brown, Ian R; Juodeikis, Rokas; Frank, Stefanie; Warren, Martin J

    2016-07-01

    Bacterial microcompartments (BMCs) enhance the breakdown of metabolites such as 1,2-propanediol (1,2-PD) to propionic acid. The encapsulation of proteins within the BMC is mediated by the presence of targeting sequences. In an attempt to redesign the Pdu BMC into a 1,2-PD synthesising factory using glycerol as the starting material we added N-terminal targeting peptides to glycerol dehydrogenase, dihydroxyacetone kinase, methylglyoxal synthase and 1,2-propanediol oxidoreductase to allow their inclusion into an empty BMC. 1,2-PD producing strains containing the fused enzymes exhibit a 245% increase in product formation in comparison to un-tagged enzymes, irrespective of the presence of BMCs. Tagging of enzymes with targeting peptides results in the formation of dense protein aggregates within the cell that are shown by immuno-labelling to contain the vast majority of tagged proteins. It can therefore be concluded that these protein inclusions are metabolically active and facilitate the significant increase in product formation.

  16. Effect of post space preparation on the sealing ability of mineral trioxide aggregate and Gutta-percha: A bacterial leakage study

    PubMed Central

    Metgud, Sandeep S; Shah, Harsh H; Hiremath, Hemalatha T; Agarwal, Deepali; Reddy, Kartik

    2015-01-01

    Aim: The purpose of this study was to evaluate the effect of post space preparation on the sealing ability of teeth obturated with mineral trioxide aggregate (MTA) and Gutta-percha. Materials and Methods: Fifty intact human mandibular premolars, after decoronation and biomechanical preparation, were randomly divided into three experimental groups. In Group A (n = 10), the canals were obturated with Gutta-percha using cold lateral compaction technique, followed by immediate post space preparation. In Group B (n = 10), the canals were obturated with 8 mm of MTA and in Group C (n = 10), sectional obturation with 4 mm of MTA was done, followed by delayed post space preparation. All specimens were subjected to bacterial leakage analysis, and the occurrence of turbidity was checked. Results: All specimens in the lateral compaction group leaked. The mean number of days at which leakage was observed in Groups A, B and C were 18.5 days, 93.6 days and 95.5 days. Conclusions: MTA can be considered as an alternative to Gutta-percha as an apical third restorative material for teeth indicated for post and core, as it demonstrates better-sealing ability compared with Gutta-percha. Further, the removal of set MTA for post space preparation does not disrupt the integrity of the remaining apical MTA. PMID:26180414

  17. Influence of tetracycline on the microbial community composition and activity of nitrifying biofilms.

    PubMed

    Matos, Maria; Pereira, Maria A; Parpot, Pier; Brito, António G; Nogueira, Regina

    2014-12-01

    The present work aims to evaluate the bacterial composition and activity (carbon and nitrogen removal) of nitrifying biofilms exposed to 50 μg L(-1) of tetracycline. The tetracycline removal efficiency and the occurrence of tetracycline resistance (tet) genes were also studied. Two sequencing batch biofilm reactors (SBBRs) fed with synthetic wastewater were operated without (SBBR1) and with (SBBR2) the antibiotic. Both SBBRs showed similar organic matter biodegradation and nitrification activity. Tetracycline removal was about 28% and biodegradation was probably the principal removal mechanism of the antibiotic. Polymerase chain reaction-denaturing gradient gel electrophoresis analysis of the bacterial community showed shifts leading to not only the fading of some ribotypes, but also the emergence of new ones in the biofilm with tetracycline. The study of the tet genes showed that tet(S) was only detected in the biofilm with tetracycline, suggesting a relationship between its occurrence and the presence of the antibiotic. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Variation in Heterotrophic and Autotrophic Nitrifier Populations in Relation to Nitrification in Organic Soils †

    PubMed Central

    Tate, Robert L.

    1980-01-01

    The occurrence of heterotrophic and autotrophic nitrifiers in Pahokee muck and the role of these organisms in the ecosystem were assessed by surveying their population densities under different field conditions and by observing the relationship of these populations with aerobic bacteria and soil moisture. Heterotrophic nitrifier populations varied from 2.0 × 105 to 3.8 × 106 bacteria per cm3 of muck in surface fallow (bare) Pahokee muck during the annual cycle. This population decreased 40-fold between the surface and the 60- to 70-cm depths of soil. Similar variations were noted with autotrophic nitrifier populations. Significant correlations were found between heterotrophic nitrifiers and both soil moisture and aerobic bacteria. These relationships did not exist for the autotrophic nitrifiers. In soil that had been heated to kill the autotrophic nitrifiers, while preserving a population of the heterotrophs, and then amended with sodium acetate or ammonium sulfate or both, no nitrate or nitrite accumulated, although significant increases in heterotrophic nitrifiers were detected. In unheated control soil, nitrate plus nitrite-N increased from 14.3 to 181 μg/g of wet soil, and 48 μg of nitrite-N per g was produced. These data suggest that the autotrophic nitrifiers were the sole population responsible for nitrification in Pahokee muck. PMID:16345599

  19. Substrate interactions during trichloroethene degradation by nitrifying cultures

    SciTech Connect

    Ochoa, M.H.; Hughes, J.B.

    1994-12-31

    Studies have been conducted assessing the influence of competitive substrate interactions on the rate/extent of trichloroethene degradation by nitrifying mixed cultures. Specifically, the effect of ammonia, hydroxylamine, tetrachloroethene and cis-dichloroethene have been examined. Results demonstrate that rates of degradation and finite transformation capacity are significantly influenced by these interactions. Adding hydroxylamine as an exogenous source of energy in the absence of the primary substrate produced an increase in the degradation capacity of these cultures up to threefold. Models are being tested to predict these phenomena.

  20. The effects of salinity on nitrification using halophilic nitrifiers in a Sequencing Batch Reactor treating hypersaline wastewater

    PubMed Central

    Cui, You-Wei; Zhang, Hong-Yu; Ding, Jie-Ran; Peng, Yong-Zhen

    2016-01-01

    With annual increases in the generation and use of saline wastewater, the need to avoid environmental problems such as eutrophication is critical. A previous study identified ways to start up a halophilic sludge domesticated from estuarine sediments to remove nitrogen from wastewater with a salinity of 30 g/L. This investigation expands that work to explore the impact of salinity on nitrogen removal. This study demonstrated that the mixed halophilic consortia removed nitrogen from wastewater with a salinity of 30–85 g/L. A kinetic analysis showed that halophilic nitrifiers selected based on hypersalinity were characterized by low Ks, μmax and specific ammonium oxidization rates. This explains the decrease in ammonium removal efficiency in the high salinity operational phases. Salinity inhibited ammonia oxidizing bacteria (AOB) activity, as well as the number of dominant AOB, but did not significantly affect the AOB dominant species. Three most dominant AOB lineages in the halophilic sludge were Nitrosomonas marina, Nitrosomonas europaea, and Nitrosococcus mobilis. Nitrosomonas europaea and Nitrosococcus mobilis were mainly affected by salinity, while nitrite accumulation and ammonia loading played the key role in determining the abundance of Nitrosococcus mobilis and Nitrosococcus europaea. The study contributes insights about shifts in halophilic nitrifying bacterial populations. PMID:27109617

  1. Evaluation of natural zeolite as microorganism support medium in nitrifying batch reactors: influence of zeolite particle size.

    PubMed

    Mery, C; Guerrero, L; Alonso-Gutiérrez, J; Figueroa, M; Lema, J M; Montalvo, S; Borja, R

    2012-01-01

    An evaluation of natural zeolite as a microorganism carrier in nitrifying reactors operated in batch mode was carried out. Specifically, the influence of zeolite particle sizes of 0.5, 1.0 and 2.0 mm in diameter on microorganism adherence to zeolite, ammonium adsorption capacity and the identification of microbial populations were assessed. The greatest amount of total biomass adhered was observed for a zeolite particle size of 1 mm (0.289 g) which was achieved on the 12th day of operation. The highest ammonium adsorption capacity was observed for a zeolite particle size of 0.5 mm, which was 64% and 31% higher than that observed for particle sizes of 1.0 and 2.0 mm, respectively. The maximum de-sorption values were also found for a zeolite particle size of 0.5 mm, although when equilibrium was reached the ammonium concentrations were similar to those observed for a zeolite particle size of 1.0 mm. It was also found that the experimental data on ammonium adsorption fitted very well to the Freundlich isotherm for the three particle sizes studied. Finally, the nitrifying reactors showed similar microbial populations independently of the particle size used as microorganism carrier. The dominant bacterial community was Gammaproteobacteria making up 80% of the total population found. Betaproteobacteria were also identified and made up 12% approx. of the total population. Ammonium Oxidant Betaproteobacteria and Nitrobacter were also detected.

  2. Quantitative response of nitrifying and denitrifying communities to environmental variables in a full-scale membrane bioreactor.

    PubMed

    Gómez-Silván, C; Vílchez-Vargas, R; Arévalo, J; Gómez, M A; González-López, J; Pieper, D H; Rodelas, B

    2014-10-01

    The abundance and transcription levels of specific gene markers of total bacteria, ammonia-oxidizing Betaproteobacteria, nitrite-oxidizing bacteria (Nitrospira-like) and denitrifiers (N2O-reducers) were analyzed using quantitative PCR (qPCR) and reverse-transcription qPCR during 9 months in a full-scale membrane bioreactor treating urban wastewater. A stable community of N-removal key players was developed; however, the abundance of active populations experienced sharper shifts, demonstrating their fast adaptation to changing conditions. Despite constituting a small percentage of the total bacterial community, the larger abundances of active populations of nitrifiers explained the high N-removal accomplished by the MBR. Multivariate analyses revealed that temperature, accumulation of volatile suspended solids in the sludge, BOD5, NH4(+) concentration and C/N ratio of the wastewater contributed significantly (23-38%) to explain changes in the abundance of nitrifiers and denitrifiers. However, each targeted group showed different responses to shifts in these parameters, evidencing the complexity of the balance among them for successful biological N-removal. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Concentrations of nitrifying bacteria in sewages, effluents, and a receiving stream and resistance of these organisms to chlorination.

    PubMed Central

    Strom, P F; Matulewich, V A; Finstein, M S

    1976-01-01

    Estimates of NH4+-and NO2-oxidizers in samples from four activated sludge plants treating mainly domestic sewage were obtained using a most-probable-number (MPN) technique. Ranges of concentrations per milliliter of each, respectively, were 1,010 to 3,880 and 79 to 145 in settled sewages, 32 to 7,420 and 2 to 1,010 in secondary effluents, and less than 0.1 to 622 and 0.1 to 70 in chlorinated secondary effluents. The results of this field study indicated that nitrifiers were more resistant to chlorination than fecal streptococci, which were also enumerated. In laboratory studies the survivals of these bacterial groups in secondary effluents were determined after exposure to chlorine residuals of up to 2 mg/liter for 0 to 60 min. The nitrifiers proved considerably more resistant than fecal streptococci, with NO2-oxidizers showing greater resistance than NH4+-oxidizers. Below the outfall of one of the plants that discharges heavily chlorinated unnitrified effluent, NH4+-oxidizers amounted to approximately 200 X 10(5) per g of slime scraped from stream-bed rocks. Upstream of the outfall this was approximatley 3 X 10(5)/G. PMID:818958

  4. Soil environmental conditions and microbial build-up mediate the effect of plant diversity on soil nitrifying and denitrifying enzyme activities in temperate grasslands.

    PubMed

    Le Roux, Xavier; Schmid, Bernhard; Poly, Franck; Barnard, Romain L; Niklaus, Pascal A; Guillaumaud, Nadine; Habekost, Maike; Oelmann, Yvonne; Philippot, Laurent; Salles, Joana Falcao; Schloter, Michael; Steinbeiss, Sibylle; Weigelt, Alexandra

    2013-01-01

    Random reductions in plant diversity can affect ecosystem functioning, but it is still unclear which components of plant diversity (species number - namely richness, presence of particular plant functional groups, or particular combinations of these) and associated biotic and abiotic drivers explain the observed relationships, particularly for soil processes. We assembled grassland communities including 1 to 16 plant species with a factorial separation of the effects of richness and functional group composition to analyze how plant diversity components influence soil nitrifying and denitrifying enzyme activities (NEA and DEA, respectively), the abundance of nitrifiers (bacterial and archaeal amoA gene number) and denitrifiers (nirK, nirS and nosZ gene number), and key soil environmental conditions. Plant diversity effects were largely due to differences in functional group composition between communities of identical richness (number of sown species), though richness also had an effect per se. NEA was positively related to the percentage of legumes in terms of sown species number, the additional effect of richness at any given legume percentage being negative. DEA was higher in plots with legumes, decreased with increasing percentage of grasses, and increased with richness. No correlation was observed between DEA and denitrifier abundance. NEA increased with the abundance of ammonia oxidizing bacteria. The effect of richness on NEA was entirely due to the build-up of nitrifying organisms, while legume effect was partly linked to modified ammonium availability and nitrifier abundance. Richness effect on DEA was entirely due to changes in soil moisture, while the effects of legumes and grasses were partly due to modified nitrate availability, which influenced the specific activity of denitrifiers. These results suggest that plant diversity-induced changes in microbial specific activity are important for facultative activities such as denitrification, whereas changes

  5. Soil Environmental Conditions and Microbial Build-Up Mediate the Effect of Plant Diversity on Soil Nitrifying and Denitrifying Enzyme Activities in Temperate Grasslands

    PubMed Central

    Le Roux, Xavier; Schmid, Bernhard; Poly, Franck; Barnard, Romain L.; Niklaus, Pascal A.; Guillaumaud, Nadine; Habekost, Maike; Oelmann, Yvonne; Philippot, Laurent; Salles, Joana Falcao; Schloter, Michael; Steinbeiss, Sibylle; Weigelt, Alexandra

    2013-01-01

    Random reductions in plant diversity can affect ecosystem functioning, but it is still unclear which components of plant diversity (species number – namely richness, presence of particular plant functional groups, or particular combinations of these) and associated biotic and abiotic drivers explain the observed relationships, particularly for soil processes. We assembled grassland communities including 1 to 16 plant species with a factorial separation of the effects of richness and functional group composition to analyze how plant diversity components influence soil nitrifying and denitrifying enzyme activities (NEA and DEA, respectively), the abundance of nitrifiers (bacterial and archaeal amoA gene number) and denitrifiers (nirK, nirS and nosZ gene number), and key soil environmental conditions. Plant diversity effects were largely due to differences in functional group composition between communities of identical richness (number of sown species), though richness also had an effect per se. NEA was positively related to the percentage of legumes in terms of sown species number, the additional effect of richness at any given legume percentage being negative. DEA was higher in plots with legumes, decreased with increasing percentage of grasses, and increased with richness. No correlation was observed between DEA and denitrifier abundance. NEA increased with the abundance of ammonia oxidizing bacteria. The effect of richness on NEA was entirely due to the build-up of nitrifying organisms, while legume effect was partly linked to modified ammonium availability and nitrifier abundance. Richness effect on DEA was entirely due to changes in soil moisture, while the effects of legumes and grasses were partly due to modified nitrate availability, which influenced the specific activity of denitrifiers. These results suggest that plant diversity-induced changes in microbial specific activity are important for facultative activities such as denitrification, whereas

  6. Biotransformation of acyclovir by an enriched nitrifying culture.

    PubMed

    Xu, Yifeng; Yuan, Zhiguo; Ni, Bing-Jie

    2017-03-01

    This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L(-1) and 15 μg L(-1)). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium. The positive correlation was found between acyclovir degradation rate and ammonia oxidation rate, confirming the cometabolism of acyclovir by the enriched nitrifying culture in the presence of ammonium. Formation of the product carboxy-acyclovir (P239) indicated the main biotransformation pathway was aerobic oxidation of the terminal hydroxyl group, which was independent on the metabolic type (i.e. cometabolism or metabolism). This enzyme-linked reaction might be catalyzed by monooxygenase from ammonia oxidizing bacteria or heterotrophs. The formation of carboxy-acyclovir was demonstrated to be irrelevant to the acyclovir concentrations applied, indicating the revealed biotransformation pathway might be the dominant removal pathway of acyclovir in wastewater treatment.

  7. Ammonia removal from prawn aquaculture water using immobilized nitrifying bacteria.

    PubMed

    Shan, H; Obbard, J P

    2001-12-01

    Intensive prawn aquaculture in tropical regions is associated with high concentrations of total ammoniacal nitrogen (TAN) as a result of high rates of prawn excretion and feed loading. Excessive TAN can adversely effect productivity and result in adverse impacts on coastal waters. Cultures of indigenous nitrifying bacteria were enriched from intensive prawn aquaculture pond water using continuous and batch enrichment techniques. Cultures were capable of TAN removal over a wide range of initial TAN concentrations - up to 200 mg/l. Cultures were immobilized onto porous clay pellets to enhance cell density and applied to culture medium and TAN-augmented pond water under aerobic conditions to determine TAN removal proficiency. Immobilized cultures were able to achieve a high TAN removal proficiency in pond water--even at a low density of 0.1 pellet per liter. A concentration of less than 0.5 mg TAN/l could be maintained under a fed-batch condition of 3.2 mg TAN/l per day, after an initial 2-day lag phase. A simplified and effective culture enrichment process was developed for culture immobilization onto pellets using TAN-augmented pond water. Overall, pellet immobilization of indigenous nitrifying bacteria represents a potentially effective TAN control system for prawn aquaculture in low-cost, but intensive tropical prawn farms.

  8. Population Ecology of Nitrifiers in a Stream Receiving Geothermal Inputs of Ammonium

    PubMed Central

    Cooper, A. Bryce

    1983-01-01

    The distribution, activity, and generic diversity of nitrifying bacteria in a stream receiving geothermal inputs of ammonium were studied. The high estimated rates of benthic nitrate flux (33 to 75 mg of N · m−2 · h−1) were a result of the activity of nitrifiers located in the sediment. Nitrifying potentials and ammonium oxidizer most probable numbers in the sediments were at least one order of magnitude higher than those in the waters. Nitrifiers in the oxygenated surface (0 to 2 cm) sediments were limited by suboptimal temperature, pH, and substrate level. Nitrifiers in deep (nonsurface) oxygenated sediments did not contribute significantly to the changes measured in the levels of inorganic nitrogen species in the overlying waters and presumably derived their ammonium supply from ammonification within the sediment. Ammonium-oxidizing isolates obtained by a most-probable number nonenrichment procedure were species of either Nitrosospira or Nitrosomonas, whereas all those obtained by an enrichment procedure (i.e., selective culture) were Nitrosomonas spp. The efficiency of the most-probable-number method for enumerating ammonium oxidizers was calculated to be between 0.05 and 2.0%, suggesting that measurements of nitrifying potentials provide a better estimate of nitrifying populations. PMID:16346261

  9. The effect of sodium chloride on the two-step kinetics of the nitrifying process.

    PubMed

    Sánchez, Omar; Aspé, Estrella; Martí, María C; Roeckel, Marlene

    2004-01-01

    Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot-blot hybridization technique with 16S rRNA-targeted probes was used to determine the ammonia-oxidizing and nitrite-oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations: the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation.

  10. 3-D analysis of bacterial cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using complementary microscopy tomography approaches.

    PubMed

    Schmid, G; Zeitvogel, F; Hao, L; Ingino, P; Floetenmeyer, M; Stierhof, Y-D; Schroeppel, B; Burkhardt, C J; Kappler, A; Obst, M

    2014-07-01

    The formation of cell-(iron)mineral aggregates as a consequence of bacterial iron oxidation is an environmentally widespread process with a number of implications for processes such as sorption and coprecipitation of contaminants and nutrients. Whereas the overall appearance of such aggregates is easily accessible using 2-D microscopy techniques, the 3-D and internal structure remain obscure. In this study, we examined the 3-D structure of cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using a combination of advanced 3-D microscopy techniques. We obtained 3-D structural and chemical information on different cellular encrustation patterns at high spatial resolution (4-200 nm, depending on the method): more specifically, (1) cells free of iron minerals, (2) periplasm filled with iron minerals, (3) spike- or platelet-shaped iron mineral structures, (4) bulky structures on the cell surface, (5) extracellular iron mineral shell structures, (6) cells with iron mineral filled cytoplasm, and (7) agglomerations of extracellular globular structures. In addition to structural information, chemical nanotomography suggests a dominant role of extracellular polymeric substances (EPS) in controlling the formation of cell-(iron)mineral aggregates. Furthermore, samples in their hydrated state showed cell-(iron)mineral aggregates in pristine conditions free of preparation (i.e., drying/dehydration) artifacts. All these results were obtained using 3-D microscopy techniques such as focused ion beam (FIB)/scanning electron microscopy (SEM) tomography, transmission electron microscopy (TEM) tomography, scanning transmission (soft) X-ray microscopy (STXM) tomography, and confocal laser scanning microscopy (CLSM). It turned out that, due to the various different contrast mechanisms of the individual approaches, and due to the required sample preparation steps, only the combination of these techniques was able to provide a

  11. Autotrophic growth of nitrifying community in an agricultural soil

    PubMed Central

    Xia, Weiwei; Zhang, Caixia; Zeng, Xiaowei; Feng, Youzhi; Weng, Jiahua; Lin, Xiangui; Zhu, Jianguo; Xiong, Zhengqin; Xu, Jian; Cai, Zucong; Jia, Zhongjun

    2011-01-01

    The two-step nitrification process is an integral part of the global nitrogen cycle, and it is accomplished by distinctly different nitrifiers. By combining DNA-based stable isotope probing (SIP) and high-throughput pyrosequencing, we present the molecular evidence for autotrophic growth of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) in agricultural soil upon ammonium fertilization. Time-course incubation of SIP microcosms indicated that the amoA genes of AOB was increasingly labeled by 13CO2 after incubation for 3, 7 and 28 days during active nitrification, whereas labeling of the AOA amoA gene was detected to a much lesser extent only after a 28-day incubation. Phylogenetic analysis of the 13C-labeled amoA and 16S rRNA genes revealed that the Nitrosospira cluster 3-like sequences dominate the active AOB community and that active AOA is affiliated with the moderately thermophilic Nitrososphaera gargensis from a hot spring. The higher relative frequency of Nitrospira-like NOB in the 13C-labeled DNA suggests that it may be more actively involved in nitrite oxidation than Nitrobacter-like NOB. Furthermore, the acetylene inhibition technique showed that 13CO2 assimilation by AOB, AOA and NOB occurs only when ammonia oxidation is not blocked, which provides strong hints for the chemolithoautotrophy of nitrifying community in complex soil environments. These results show that the microbial community of AOB and NOB dominates the nitrification process in the agricultural soil tested. PMID:21326337

  12. Monochloramine Cometabolism by Mixed-Culture Nitrifiers under Drinking Water Conditions

    EPA Science Inventory

    The current research investigated monochloramine cometabolism by nitrifying mixed cultures grown under drinking water relevant conditions and harvested from sand-packed reactors before conducting suspended growth batch kinetic experiments. Three batch reactors were used in each ...

  13. Monochloramine Cometabolism by Mixed-Culture Nitrifiers under Drinking Water Conditions

    EPA Science Inventory

    The current research investigated monochloramine cometabolism by nitrifying mixed cultures grown under drinking water relevant conditions and harvested from sand-packed reactors before conducting suspended growth batch kinetic experiments. Three batch reactors were used in each ...

  14. Inability of probiotic bacterial strains Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 to induce human platelet aggregation in vitro.

    PubMed

    Zhou, J S; Rutherfurd, K J; Gill, H S

    2005-11-01

    Platelet aggregation contributes to the pathogenesis of infective endocarditis, and aggregation of platelets induced by lactobacilli is thought to be an important contributory factor in the development and progression of Lactobacillus endocarditis. The main purpose of this study was to examine the effect of immunity-enhancing probiotic strains Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 on the activation and aggregation of human blood platelets. Whole blood samples from healthy individuals were incubated in vitro with HN001 or HN019 and subsequently labeled with platelet-specific monoclonal antibodies, fluorescein isothiocyanate-conjugated anti-CD41a (expressed on normal platelets), and phycoerythrin-streptavidin-conjugated anti-CD62p (expressed on activated platelets) before analysis by flow cytometry. Platelet-rich plasma was used to assist the gating of the platelet cluster. ADP and epinephrine were used as the physiological platelet activation agonists. Platelet aggregation-inducing strain Streptococcus sanguis 133-79 was used as a positive control strain. The mean fluorescence intensity of phycoerythrin and the percentage of platelets expressing the CD62p marker were used to assess the degree of platelet activation. The percentage of CD62p-positive platelets and the light scatter profiles of the agonist-activated platelets were used to identify the occurrence and degree of platelet aggregation. HN001 and HN019 had no effect on spontaneous platelet activation and aggregation; they also failed to exacerbate the platelet aggregation activity induced by ADP and epinephrine. Therefore, these test probiotic strains HN001 and HN019 are less likely to participate in the pathogenesis of infective endocarditis or other thrombotic disorders with regard to platelet aggregation factors.

  15. Formation of nitrifying biofilms on small suspended particles in airlift reactors.

    PubMed

    Tijhuis, L; Huisman, J L; Hekkelman, H D; van Loosdrecht, M C; Heijnen, J J

    1995-09-05

    For a stable and reliable operation of a BAS-reactor a high, active biomass concentration is required with mainly biofilm-covered carriers. The effect of reactor conditions on the formation of nitrifying biofilms in BAS-reactors was investigated in this article. A start-up strategy to obtain predominantly biofilm-covered carriers, based on the balancing of detachment and a biomass production per carrier surface area, proved tp be very successful. The amount of biomass and the fraction of covered carrier were high and development of nitrification activity was fast, leading to a volumetric conversion of 5 kg(N) . m(-3) . d(-1) at a hydraulic retention time of 1h. A 1-week, continuous inoculation with suspended purely nitrifying microorganisms resulted in a swift start-up compared with batch addition of a small number of biofilms with some nitrification activity. The development of nitrifying biofilms was very similar to the formation of heterotrophic biofilms. In contrast to heterotrophic bio-films, the diameter of nitrifying biofilms increased during start-up. The detachment rate from nitrifying biofilms decreased with lower concentrations of bare carrier, in a fashion comparable with heterotrophic biofilms, but the nitrifying biofilms were much more robust and resistant. Standard diffusion theory combined with reaction kinetics are capable of predicting the activity and conversion of biofilms on small suspended particles. (c) 1995 John Wiley & Sons Inc.

  16. Enhanced biodegradation of phenolic compounds in landfill leachate by enriched nitrifying membrane bioreactor sludge.

    PubMed

    Boonyaroj, Varinthorn; Chiemchaisri, Chart; Chiemchaisri, Wilai; Yamamoto, Kazuo

    2017-02-05

    The role of autotrophic nitrification on the biodegradation of toxic organic micro-pollutants presented in landfill leachate was assessed. A two-stage MBR system consisting of an inclined tube incorporated anoxic reactor followed by aerobic submerged membrane reactor was operated under long sludge age condition in which nitrifying bacteria could be enriched. During the reactor operation, organic removal efficiencies were more than 90% whereas phenolic compounds including bisphenol A (BPA) and 4-methyl-2,6-di-tert-butylphenol (BHT) were removed by 65 and 70% mainly through biodegradation in the aerobic reactor even at high feed concentrations of 1000μg/L for both compounds. Batch experiments revealed that enriched nitrifying sludge with nitrifying activities could biodegraded 88 and 75% of BPA and BHT, largely improved from non-nitrifying sludge and enriched nitrifying sludge with the presence of inhibitor. The first-order kinetic rates of BHT and BPA removal were 0.0108 and 0.096h(-1), also enhanced by 44% from the non-nitrifying sludge.

  17. Emergent macrophytes select for nitrifying and denitrifying microorganisms in constructed wetlands

    NASA Astrophysics Data System (ADS)

    Trias, Rosalia; Ramió Pujol, Sara; Bañeras, Lluis

    2014-05-01

    The use of constructed wetlands for wastewater treatment is a reliable low-cost alternative that has been widely developed during the last years. Several processes involving plants, sediments, and microbial communities contribute to nitrogen removal in wetlands. Vegetation plays an important role in this process, not only by nutrient assimilation but also by the stimulation of the plant associated microbiota. Plants supply oxygen at the close proximity of the root surface that may favour ammonia oxidizers. At the same time, exudation of organic compounds potentially speeds-up denitrification in the anoxic environment. The aim of this work was to understand the plant-microbe interactions at the root level in the Empuriabrava free water surface constructed wetland (Spain). The roots of the macrophytes Typha latifolia, Typha angustifolia, Phragmites australis and Bolboschoenus maritimus were sampled at four dates from January to September 2012, covering all the stages of plant growth. Additionally, sediment surrounding vegetation and non-vegetated sediments were sampled. Microbial community structure was analysed by pyrosequencing of bacterial and archaeal 16S rDNA and functional genes (nirK, nirS, nosZ and amoA). Bacterial communities were significantly different in sediments of the vegetated areas compared to the root surface. Plant roots exhibited a higher proportion of proteobacteria whereas Actinobacteria were dominant in sediments. The nitrifiers Nitrosomonas sp. and Nitrosococcus sp. accounted for less than 1% of all sequences. Archaeal communities were dominated by the Miscellaneous Crenarchaeotic Groups C2 and C3 and Methanomicrobia. Higher relative abundances of MCG were found in roots of P. australis, B. maritimus and T. angustifolia. Ammonia oxidizing archaea accounted for less than 0.1% of all sequences but were consistently more abundant in sediment samples compared to roots. NirK and NirS-type bacterial communities showed clearly distinct distribution

  18. Relative contribution of ammonia oxidizing bacteria and other members of nitrifying activated sludge communities to micropollutant biotransformation.

    PubMed

    Men, Yujie; Achermann, Stefan; Helbling, Damian E; Johnson, David R; Fenner, Kathrin

    2017-02-01

    Improved micropollutant (MP) biotransformation during biological wastewater treatment has been associated with high ammonia oxidation activities, suggesting co-metabolic biotransformation by ammonia oxidizing bacteria as an underlying mechanism. The goal of this study was to clarify the contribution of ammonia oxidizing bacteria to increased MP degradation in nitrifying activated sludge (NAS) communities using a series of inhibition experiments. To this end, we treated a NAS community with two different ammonia oxidation inhibitors, namely octyne (OCT), a mechanistic inhibitor that covalently binds to ammonia monooxygenases, and allylthiourea (ATU), a copper chelator that depletes copper ions from the active center of ammonia monooxygenases. We investigated the biotransformation of 79 structurally different MPs by the inhibitor-treated and untreated sludge communities. Fifty-five compounds exhibited over 20% removal in the untreated control after a 46 h-incubation. Of these, 31 compounds were significantly inhibited by either ATU and/or OCT. For 17 of the 31 MPs, the inhibition by ATU at 46 h was substantially higher than by OCT despite the full inhibition of ammonia oxidation by both inhibitors. This was particularly the case for almost all thioether and phenylurea compounds tested, suggesting that in nitrifying activated sludge communities, ATU does not exclusively act as an inhibitor of bacterial ammonia oxidation. Rather, ATU also inhibited enzymes contributing to MP biotransformation but not to bulk ammonia oxidation. Thus, inhibition studies with ATU tend to overestimate the contribution of ammonia-oxidizing bacteria to MP biotransformation in nitrifying activated sludge communities. Biolog tests revealed only minor effects of ATU on the heterotrophic respiration of common organic substrates by the sludge community, suggesting that ATU did not affect enzymes that were essential in energy conservation and central metabolism of heterotrophs. By comparing ATU

  19. Protein Aggregation in a Mutant Deficient in YajL, the Bacterial Homolog of the Parkinsonism-associated Protein DJ-1

    PubMed Central

    Kthiri, Fatoum; Le, Hai-Tuong; Gautier, Valérie; Caldas, Teresa; Malki, Abderrahim; Landoulsi, Ahmed; Bohn, Chantal; Bouloc, Philippe; Richarme, Gilbert

    2010-01-01

    YajL is the closest prokaryotic homolog of the parkinsonism-associated protein DJ-1 (40% sequence identity and similar three-dimensional structure), a protein of unknown function involved in the cellular response to oxidative stress. We report here that a yajL mutant of Escherichia coli displays an increased sensitivity to oxidative stress. It also exhibits a protein aggregation phenotype in aerobiosis, but not in anaerobiosis or in aerobic cells overexpressing superoxide dismutase, suggesting that protein aggregation depends on the presence of reactive oxygen species produced by respiratory chains. The protein aggregation phenotype of the yajL mutant, which can be rescued by the wild-type yajL gene, but not by the corresponding cysteine 106 mutant allele, is similar to that of multiple mutants deficient in superoxide dismutases and catalases, although intracellular hydrogen peroxide levels were not increased in the yajL mutant, suggesting that protein aggregation in this strain does not result from a hydrogen peroxide detoxification defect. Aggregation-prone proteins included 17 ribosomal proteins, the ATP synthase β subunit, flagellin, and the outer membrane proteins OmpA and PAL; all of them are part of multiprotein complexes, suggesting that YajL might be involved in optimal expression of these complexes, especially during oxidative stress. YajL stimulated the renaturation of urea-unfolded citrate synthase and the solubilization of the urea-unfolded ribosomal proteins S1 and L3 and was more efficient as a chaperone in its oxidized form than in its reduced form. The mRNA levels of several aggregated proteins of the yajL mutant were severely affected, suggesting that YajL also acts at the level of gene expression. These two functions of YajL might explain the protein aggregation phenotype of the yajL mutant. PMID:20124404

  20. Effects of elevated CO2 concentrations on denitrifying and nitrifying popualtions at terrestrial CO2 leakeage analogous sites

    NASA Astrophysics Data System (ADS)

    Christine, Dictor Marie; Catherine, Joulian; Valerie, Laperche; Stephanie, Coulon; Dominique, Breeze

    2010-05-01

    CO2 capture and geological storage (CCS) is recognized to be an important option for carbon abatement in Europe. One of the risks of CCS is the leakage from storage site. A laboratory was conducted on soil samples sampled near-surface from a CO2 leakage analogous site (Latera, Italy) in order to evaluate the impact of an elevated soil CO2 concentration on terrestrial bacterial ecosystems form near surface terrestrial environments and to determine a potential bacterial indicator of CO2 leakage from storage site. Surveys were conducted along a 50m long transect across the vent centre, providing a spectrum of CO2 flux rates, soil gas concentrations and compositions (Beaubien et al., 2007). A bacterial diversity studies, performed by CE-SSCP technique, on a soil profile with increasing CO2 soil concentrations (from 0.3% to 100%) showed that a change on bacterial diversity was noted when CO2 concentration was above 50 % of CO2. From this result, 3 soil samples were taken at 70 cm depth in 3 distinct zones (background soil CO2 content, soil CO2 content of 20% and soil CO2 content of 50%). Then theses soil samples were incubated under closed jars flushed with different air atmospheres (20, 50 and 90 % of CO2) during 18 months. At initial, 3, 6, 12 and 18 months, some soil samples were collected in order to estimate the denitrifying, nitrifying activities as a function of CO2 concentration content and times. Theses enzymatic activities were chosen because one occurs under anaerobic conditions (denitrification) and the other occurs under aerobic conditions (nitrification). Both of them were involved in the nitrogen cycle and are major actors of soil function and groundwater quality preservation. Metabolic diversity using BIOLOG Ecoplates was determined on every soil samples. Physico-chemical parameters (e.g. pH, bulk chemistry, mineralogy) were analyzed to have some information about the evolution of the soil during the incubation with increasing soil CO2 concentrations

  1. Diversity, Abundance, and Potential Activity of Nitrifying and Nitrate-Reducing Microbial Assemblages in a Subglacial Ecosystem ▿ †

    PubMed Central

    Boyd, Eric S.; Lange, Rachel K.; Mitchell, Andrew C.; Havig, Jeff R.; Hamilton, Trinity L.; Lafrenière, Melissa J.; Shock, Everett L.; Peters, John W.; Skidmore, Mark

    2011-01-01

    Subglacial sediments sampled from beneath Robertson Glacier (RG), Alberta, Canada, were shown to harbor diverse assemblages of potential nitrifiers, nitrate reducers, and diazotrophs, as assessed by amoA, narG, and nifH gene biomarker diversity. Although archaeal amoA genes were detected, they were less abundant and less diverse than bacterial amoA, suggesting that bacteria are the predominant nitrifiers in RG sediments. Maximum nitrification and nitrate reduction rates in microcosms incubated at 4°C were 280 and 18.5 nmol of N per g of dry weight sediment per day, respectively, indicating the potential for these processes to occur in situ. Geochemical analyses of subglacial sediment pore waters and bulk subglacial meltwaters revealed low concentrations of inorganic and organic nitrogen compounds. These data, when coupled with a C/N atomic ratio of dissolved organic matter in subglacial pore waters of ∼210, indicate that the sediment communities are N limited. This may reflect the combined biological activities of organic N mineralization, nitrification, and nitrate reduction. Despite evidence of N limitation and the detection of nifH, we were unable to detect biological nitrogen fixation activity in subglacial sediments. Collectively, the results presented here suggest a role for nitrification and nitrate reduction in sustaining microbial life in subglacial environments. Considering that ice currently covers 11% of the terrestrial landmass and has covered significantly greater portions of Earth at times in the past, the demonstration of nitrification and nitrate reduction in subglacial environments furthers our understanding of the potential for these environments to contribute to global biogeochemical cycles on glacial-interglacial timescales. PMID:21622799

  2. Diversity, abundance, and potential activity of nitrifying and nitrate-reducing microbial assemblages in a subglacial ecosystem.

    PubMed

    Boyd, Eric S; Lange, Rachel K; Mitchell, Andrew C; Havig, Jeff R; Hamilton, Trinity L; Lafrenière, Melissa J; Shock, Everett L; Peters, John W; Skidmore, Mark

    2011-07-01

    Subglacial sediments sampled from beneath Robertson Glacier (RG), Alberta, Canada, were shown to harbor diverse assemblages of potential nitrifiers, nitrate reducers, and diazotrophs, as assessed by amoA, narG, and nifH gene biomarker diversity. Although archaeal amoA genes were detected, they were less abundant and less diverse than bacterial amoA, suggesting that bacteria are the predominant nitrifiers in RG sediments. Maximum nitrification and nitrate reduction rates in microcosms incubated at 4°C were 280 and 18.5 nmol of N per g of dry weight sediment per day, respectively, indicating the potential for these processes to occur in situ. Geochemical analyses of subglacial sediment pore waters and bulk subglacial meltwaters revealed low concentrations of inorganic and organic nitrogen compounds. These data, when coupled with a C/N atomic ratio of dissolved organic matter in subglacial pore waters of ~210, indicate that the sediment communities are N limited. This may reflect the combined biological activities of organic N mineralization, nitrification, and nitrate reduction. Despite evidence of N limitation and the detection of nifH, we were unable to detect biological nitrogen fixation activity in subglacial sediments. Collectively, the results presented here suggest a role for nitrification and nitrate reduction in sustaining microbial life in subglacial environments. Considering that ice currently covers 11% of the terrestrial landmass and has covered significantly greater portions of Earth at times in the past, the demonstration of nitrification and nitrate reduction in subglacial environments furthers our understanding of the potential for these environments to contribute to global biogeochemical cycles on glacial-interglacial timescales.

  3. Performance and biofilm activity of nitrifying biofilters removing trihalomethanes.

    PubMed

    Wahman, David G; Katz, Lynn E; Speitel, Gerald E

    2011-02-01

    Nitrifying biofilters seeded with three different mixed-culture sources removed trichloromethane (TCM) and dibromochloromethane (DBCM) with removals reaching 18% for TCM and 75% for DBCM. In addition, resuspended biofilm removed TCM, bromodichloromethane (BDCM), DBCM, and tribromomethane (TBM) in backwash batch kinetic tests, demonstrating that the biofilters contained organisms capable of biotransforming the four regulated trihalomethanes (THMs) commonly found in treated drinking water. Upon the initial and subsequent increased TCM addition, total ammonia nitrogen (TOTNH(3)) removal decreased and then reestablished, indicating an adjustment by the biofilm bacteria. In addition, changes in DBCM removal indicated a change in activity related to DBCM. The backwash batch kinetic tests provided a useful tool to evaluate the biofilm's bacteria. Based on these experiments, the biofilters contained bacteria with similar THM removal kinetics to those seen in previous batch kinetic experiments. Overall, performance or selection does not seem based specifically on nutrients, source water, or source cultures and most likely results from THM product toxicity, and the use of GAC media appeared to offer benefits over anthracite for biofilter stability and long-term performance, although the reasons for this advantage are not apparent based on research to date.

  4. Design Model Parameter Analysis for Nitrifying Trickling Filters.

    PubMed

    Coats, Erik R

    Nitrifying trickling filters (NTFs) represent an effective technology for water resource recovery facilities (WRRFs) to achieve compliance with ammonia-N permits. However, while the potential benefits of NTFs are many, the design methods and associated parameter databases are underdeveloped. Research herein focused on analysis of pilot-scale NTF data to develop enhanced design guidance. rn(max,0) values ranged from 1.19-3.38 gN m(-2)*d(-1), and correlated with influent ammonia-N concentration and loading. The transition concentration from rn(max,0) ranged from 0.9-22.2 mgN/L, and correlated with ammonia-N loading. Zero-order nitrification ranging from 0.24-1.58 gN m(-2)*d(-1) was observed down-gradient of rn(max,0). First-order nitrification was not observed, nor was there a strong exponential correlation for decreasing nitrification rate. To translate results to NTF media different from that utilized, a relationship between the NTF media effectiveness parameter, E, and rn(max,0) was established. Collectively, the data presented enhances the engineer's ability to model and design NTFs.

  5. Impacts of different N management regimes on nitrifier and denitrifier communities and N cycling in soil microenvironments

    PubMed Central

    Kong, Angela Y. Y.; Hristova, Krassimira; Scow, Kate M.; Six, Johan

    2011-01-01

    hypothesis was also not corroborated because canonical correspondence analyses revealed that AOB and denitrifier abundances were decoupled from potential gross N mineralization and nitrification rates and from inorganic N concentrations. Our third hypothesis was supported by the overall larger nitrifier, denitrifier, and total bacterial communities measured in the soil microaggregates compared to the cPOM and silt-and-clay. These results suggest that the microaggregates are microenvironments that preferentially stabilize C, and concomitantly promote the growth of nitrifier and denitrifier communities, thereby serving as potential hotspots for N2O losses. PMID:21339865

  6. Selective isolation of ammonia-oxidizing bacteria from autotrophic nitrifying granules by applying cell-sorting and sub-culturing of microcolonies.

    PubMed

    Fujitani, Hirotsugu; Kumagai, Asami; Ushiki, Norisuke; Momiuchi, Kengo; Tsuneda, Satoshi

    2015-01-01

    Nitrification is a key process in the biogeochemical nitrogen cycle and biological wastewater treatment that consists of two stepwise reactions, ammonia oxidation by ammonia-oxidizing bacteria (AOB) or archaea followed by nitrite oxidation by nitrite-oxidizing bacteria. One of the representatives of the AOB group is Nitrosomonas mobilis species. Although a few pure strains of this species have been isolated so far, approaches to their preservation in pure culture have not been established. Here, we report isolation of novel members of the N. mobilis species from autotrophic nitrifying granules used for ammonia-rich wastewater treatment. We developed an isolation method focusing on microcolonies formation of nitrifying bacteria. Two kinds of distinctive light scattering signatures in a cell-sorting system enabled to separate microcolonies from single cells and heterogeneous aggregates within granule samples. Inoculation of a pure microcolony into 96-well microtiter plates led to successful sub-culturing and increased probability of isolation. Obtained strain Ms1 is cultivated in the liquid culture with relatively high ammonia or nitrite concentration, not extremely slow growing. Considering environmental clones that were closely related to N. mobilis and detected in various environments, the availability of this novel strain would facilitate to reveal this member's ecophysiology in a variety of habitats.

  7. Selective isolation of ammonia-oxidizing bacteria from autotrophic nitrifying granules by applying cell-sorting and sub-culturing of microcolonies

    PubMed Central

    Fujitani, Hirotsugu; Kumagai, Asami; Ushiki, Norisuke; Momiuchi, Kengo; Tsuneda, Satoshi

    2015-01-01

    Nitrification is a key process in the biogeochemical nitrogen cycle and biological wastewater treatment that consists of two stepwise reactions, ammonia oxidation by ammonia-oxidizing bacteria (AOB) or archaea followed by nitrite oxidation by nitrite-oxidizing bacteria. One of the representatives of the AOB group is Nitrosomonas mobilis species. Although a few pure strains of this species have been isolated so far, approaches to their preservation in pure culture have not been established. Here, we report isolation of novel members of the N. mobilis species from autotrophic nitrifying granules used for ammonia-rich wastewater treatment. We developed an isolation method focusing on microcolonies formation of nitrifying bacteria. Two kinds of distinctive light scattering signatures in a cell-sorting system enabled to separate microcolonies from single cells and heterogeneous aggregates within granule samples. Inoculation of a pure microcolony into 96-well microtiter plates led to successful sub-culturing and increased probability of isolation. Obtained strain Ms1 is cultivated in the liquid culture with relatively high ammonia or nitrite concentration, not extremely slow growing. Considering environmental clones that were closely related to N. mobilis and detected in various environments, the availability of this novel strain would facilitate to reveal this member’s ecophysiology in a variety of habitats. PMID:26528282

  8. Intensified nitrogen removal in immobilized nitrifier enhanced constructed wetlands with external carbon addition.

    PubMed

    Wang, Wei; Ding, Yi; Wang, Yuhui; Song, Xinshan; Ambrose, Richard F; Ullman, Jeffrey L

    2016-10-01

    Nitrogen removal performance response of twelve constructed wetlands (CWs) to immobilized nitrifier pellets and different influent COD/N ratios (chemical oxygen demand: total nitrogen in influent) were investigated via 7-month experiments. Nitrifier was immobilized on a carrier pellet containing 10% polyvinyl alcohol (PVA), 2.0% sodium alginate (SA) and 2.0% calcium chloride (CaCl2). A batch experiment demonstrated that 73% COD and 85% ammonia nitrogen (NH4-N) were degraded using the pellets with immobilized nitrifier cells. In addition, different carbon source supplement strategies were applied to remove the nitrate (NO3-N) transformed from NH4-N. An increase in COD/N ratio led to increasing reduction in NO3-N. Efficient nitrification and denitrification promoted total nitrogen (TN) removal in immobilized nitrifier biofortified constructed wetlands (INB-CWs). The results suggested that immobilized nitrifier pellets combined with high influent COD/N ratios could effectively improve the nitrogen removal performance in CWs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Occurrence of nitrifying bacteria and nitrification in Finnish drinking water distribution systems.

    PubMed

    Lipponen, Mari T T; Suutari, Merja H; Martikainen, Pertti J

    2002-10-01

    Microbiological nitrification process may lead to chemical, microbiological and technical problems in drinking water distribution systems. Nitrification activity is regulated by several physical, and chemical, and operational factors. However, the factors affecting nitrification in the distribution systems in boreal region, having its specific environmental characteristics, are poorly known. We studied the occurrence and activity of nitrifying bacteria in 15 drinking water networks distributing water with very different origin and treatment practices. The waters included chloraminated surface water, chlorinated surface water, and non-disinfected groundwater. The networks were located in eight towns in different parts of Finland. Our results showed that nitrifying bacteria are common in boreal drinking water distribution systems despite their low temperature. Surprisingly high numbers and activities of nitrifiers were detected in pipeline sediment samples. The numbers of ammonia-oxidizing bacteria and their oxidation potentials were highest in chloraminated drinking water delivering networks, whereas the nitrite-oxidizing bacteria were present in the greatest numbers in those networks that used non-disinfected groundwater. The occurrence of nitrifying bacteria in drinking water samples correlated positively with the numbers of heterotrophic bacteria and turbidity, and negatively with the content of total chlorine. Although nitrifying bacteria grew well in drinking water distribution systems, the problems with nitrite accumulation are rare in Finland.

  10. Rapid formation of nitrifying granules treating high-strength ammonium wastewater in a sequencing batch reactor.

    PubMed

    Chen, Fang-Yuan; Liu, Yong-Qiang; Tay, Joo-Hwa; Ning, Ping

    2015-05-01

    Short initial settling time and rapidly increased ammonium nitrogen loading were employed to cultivate nitrifying granular sludge treating inorganic wastewater with 1000 mg/L ammonium nitrogen. It was found that the nitrifying granule-dominant sludge was formed in a sequencing batch reactor (SBR) with influent ammonium concentration increased from 200 to 1000 mg N/L within 55 days. During the following 155-day operation period, nitrifying granules exhibited good performance with an ammonium removal efficiency of 99%. In the meantime, sludge volume index (SVI) decreased from 92 to 15 mL/g and the mean size of the nitrifying granules increased from 106 to 369 μm. Mixed liquor suspended solids (MLSS) decreased from the initial 6.4 to around 3 g/L during the granulation period and increased to over 10 g/L at the end of the operation. The long-term stability of nitrifying granules and the reactor performance were not negatively affected by inhibition from free ammonia (FA) and free nitrous acid (FNA) in this study. This makes the granule sludge technology promising in treating high-strength ammonium wastewater in practice.

  11. Influence of water quality on nitrifier regrowth in two full-scale drinking water distribution systems.

    PubMed

    Scott, Daniel B; Van Dyke, Michele I; Anderson, William B; Huck, Peter M

    2015-12-01

    The potential for regrowth of nitrifying microorganisms was monitored in 2 full-scale chloraminated drinking water distribution systems in Ontario, Canada, over a 9-month period. Quantitative PCR was used to measure amoA genes from ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), and these values were compared with water quality parameters that can influence nitrifier survival and growth, including total chlorine, ammonia, temperature, pH, and organic carbon. Although there were no severe nitrification episodes, AOB and AOA were frequently detected at low concentrations in samples collected from both distribution systems. A culture-based presence-absence test confirmed the presence of viable nitrifiers. AOB were usually present in similar or greater numbers than AOA in both systems. As well, AOB showed higher regrowth potential compared with AOA in both systems. Statistically significant correlations were measured between several water quality parameters of relevance to nitrification. Total chlorine was negatively correlated with both nitrifiers and heterotrophic plate count (HPC) bacteria, and ammonia levels were positively correlated with nitrifiers. Of particular importance was the strong correlation between HPC and AOB, which reinforced the usefulness of HPC as an operational parameter to measure general microbiological conditions in distribution systems.

  12. [Isolation of heterotrophic nitrifiers which can tolerate high concentration of ammonia-nitrogen and the optimization of their nitrogen removal efficiency in wastewater].

    PubMed

    Si, Wen-Gong; Lü, Zhi-Gang; Xu, Chao

    2011-11-01

    The removal capabilities and tolerance of high concentration of ammonia-nitrogen of heterotrophic nitrifiers were studied. Methods included multi-point sampling, domestication, gradient dilution of domestication liquid, color indicator as rapid nitrification detection and isolation from streaking plate were conducted to screen heterotrophic nitrifiers. The strains were identified according to the sequence analysis of 16S rDNA. After inoculating the strains into ammonia-nitrogen wastewater, changes of nitrogen compounds were measured in order to understand their denitrification characteristics. The denitrification efficiency was optimized by improving the C/N ratio, changing the compatibility of the strains and mixing the compatible strains with the domesticated bacterial suspension. Finally 8 high-efficiency heterotrohic nitrifiers were obtained, and named as N1-N8 respectively. Phylogenetic analysis showed that 8 strains belonged to Comamonas genus, Rhodococcus genus, Pseudomonos genus, Arthrobacter genus and Paracoccus genus, respectively. When the initial concentration of ammonia nitrogen was 256.9 mg x L(-1) and the C/N was 5.5 of the artificial wastewater, the removal rates of ammonia nitrogen by the strains were about 65%-80%, and the stain N4 was the best. When the C/N ratio of the wastewater increased to 8.0, the ammonia nitrogen removal rates of the strains correspondingly increased to about 80% -90%. As the strains compatibility, the denitrification rate of N4 + N5 + N6 was 88.2% in the artificial wastewater with initial ammonia nitrogen concentration was 261.1 mg x L(-1) and initial C/N ratio was 5.5, which was higher than that of any single strain. The ammonia nitrogen removal rate could reach to 99.8% when N4 + N5 + N6 were combined with the domesticated bacterial suspension. In the artificial wastewater, when the initial ammonia nitrogen increased to 446.9 mg x L(-1) and the C/N ratio decreased to 3.2, the ammonia nitrogen removal rate of the mixed

  13. Stereochemical determination of chlorophyll-d molecule from Acaryochloris marina and its modification to a self-aggregative chlorophyll as a model of green photosynthetic bacterial antennae.

    PubMed

    Mizoguchi, Tadashi; Shoji, Ayumi; Kunieda, Michio; Miyashita, Hideaki; Tsuchiya, Tohru; Mimuro, Mamoru; Tamiaki, Hitoshi

    2006-03-01

    Acaryochloris marina is a unique photosynthetic prokaryote containing chlorophyll(Chl)-d as a major photoactive pigment (over 95%). The molecular structure of Chl-d is proposed as the 3-formyl analog of Chl-a. However, the stereochemistry of Chl-d at the 13(2)-, 17- and 18-positions has not yet been established unambiguously. In the first part of this paper, we describe the determination of their stereochemistries to be 13(2)-(R)-, 17-(S)- and 18-(S)-configurations by using 1H-1H NOE correlations in 1H-NMR and circular dichroism spectra as well as chemical modification of Chl-a to produce stereochemically defined Chl derivatives. In the second part of the paper, we report a facile synthesis of a self-aggregative Chl by modifying isolated Chl-d. Since Chl-d was characterized by its reactive 3-formyl group, the formyl group was reduced with t-BuNH2BH3 to afford the desirable Chl, 3-deformyl-3-hydroxymethyl-pyrochlorophyll-d (3(1)-OH-pyroChl-d). The synthetic 3(1)-OH-pyroChl-d molecules spontaneously self-organized to form well-ordered aggregates in a non-polar organic solvent. The self-aggregates are a good model of major light-harvesting antenna systems of green photosynthetic bacteria, chlorosomes, in terms of the following three findings. (1) Both the red-shifted electronic absorption band above 750 nm and its induced reverse S-shape CD signal around 750 nm were observed in 0.5% (v/v) THF-cyclohexane. (2) The stretching mode of the 13-carbonyl group was downshifted by about 35 cm(-1) from the wavenumber of its free carbonyl. (3) The self-aggregates were quite stable on titration of pyridine to the suspension, in comparison with those of natural chlorosomal bacteriochlorophyll-d possessing the 3-(1-hydroxyethyl) group.

  14. [Study of shear rate in modified airlift nitrifying bioreactor].

    PubMed

    Jin, Ren-cun; Zheng, Ping

    2006-06-01

    The characteristics of shear rate in an airlift nitrifying bioreactor and its influencing factors were studied. The results showed that the shear rate was different in different sections of the bioreactor. With inlet gas flowrate at 430 approximately 2700 L x h(-1), the overall shear rate was (0.702 approximately 3.13) x 10(5) s(-1), shear rate in riser was (1.07 approximately 31.3) x 10(5) s(-1) and in gas-liquid separator was (1.12 approximately 25.0) x 10(5) s(-1), respectively. It indicates that the highest shear rates prevailed in the riser part of bioreactor. The operational variables and the bioreactor configurations exerted a significant influence on the shear level of the bioreactor. When inlet gas flowrate was raised from 1300 to 2700 L x h(-1), shear rate in riser and separator ascended first and then descended subsequently. The diameter of draft tube (d) was negatively correlated with shear rate. When the draft tube with diameter of 5.5 cm was installed, the shear rates in riser, separator and overall shear rate were 85.5%, 82.3% and 80.6%, respectively less as compared with that with diameter of 4.0 cm. The number of static mixers (N) was positively correlated with the shear rate. When d was set at 4.0 cm, with N of 10 and 39, the shear rates in riser were 6.14 and 7.97 times higher respectively, than that of conventional bioreactor. The ratio of maximum local shear rate to overall shear rate was 3.68 approximately 7.66, and the homogeneity of the shear field in airlift bioreactors could be improved if d and N were set at 5.5 cm and 10 approximately 13, respectively.

  15. Relative rates of nitric oxide and nitrous oxide production by nitrifiers, denitrifiers, and nitrate respirers

    NASA Technical Reports Server (NTRS)

    Anderson, I. C.; Levine, J. S.

    1986-01-01

    An account is given of the atmospheric chemical and photochemical effects of biogenic nitric and nitrous oxide emissions. The magnitude of the biogenic emission of NO is noted to remain uncertain. Possible soil sources of NO and N2O encompass nitrification by autotropic and heterotropic nitrifiers, denitrification by nitrifiers and denitrifiers, nitrate respiration by fermenters, and chemodenitrification. Oxygen availability is the primary determinant of these organisms' relative rates of activity. The characteristics of this major influence are presently investigated in light of the effect of oxygen partial pressure on NO and N2O production by a wide variety of common soil-nitrifying, denitrifying, and nitrate-respiring bacteria under laboratory conditions. The results obtained indicate that aerobic soils are primary sources only when there is sufficient moisture to furnish anaerobic microsites for denitrification.

  16. Relative rates of nitric oxide and nitrous oxide production by nitrifiers, denitrifiers, and nitrate respirers

    NASA Technical Reports Server (NTRS)

    Anderson, I. C.; Levine, J. S.

    1986-01-01

    An account is given of the atmospheric chemical and photochemical effects of biogenic nitric and nitrous oxide emissions. The magnitude of the biogenic emission of NO is noted to remain uncertain. Possible soil sources of NO and N2O encompass nitrification by autotropic and heterotropic nitrifiers, denitrification by nitrifiers and denitrifiers, nitrate respiration by fermenters, and chemodenitrification. Oxygen availability is the primary determinant of these organisms' relative rates of activity. The characteristics of this major influence are presently investigated in light of the effect of oxygen partial pressure on NO and N2O production by a wide variety of common soil-nitrifying, denitrifying, and nitrate-respiring bacteria under laboratory conditions. The results obtained indicate that aerobic soils are primary sources only when there is sufficient moisture to furnish anaerobic microsites for denitrification.

  17. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  18. The BR domain of PsrP interacts with extracellular DNA to promote bacterial aggregation; structural insights into pneumococcal biofilm formation

    PubMed Central

    Schulte, Tim; Mikaelsson, Cecilia; Beaussart, Audrey; Kikhney, Alexey; Deshmukh, Maya; Wolniak, Sebastian; Pathak, Anuj; Ebel, Christine; Löfling, Jonas; Fogolari, Federico; Henriques-Normark, Birgitta; Dufrêne, Yves F.; Svergun, Dmitri; Nygren, Per-Åke; Achour, Adnane

    2016-01-01

    The major human pathogen Streptococcus pneumoniae is a leading cause of disease and death worldwide. Pneumococcal biofilm formation within the nasopharynx leads to long-term colonization and persistence within the host. We have previously demonstrated that the capsular surface-associated pneumococcal serine rich repeat protein (PsrP), key factor for biofilm formation, binds to keratin-10 (KRT10) through its microbial surface component recognizing adhesive matrix molecule (MSCRAMM)-related globular binding region domain (BR187–385). Here, we show that BR187–385 also binds to DNA, as demonstrated by electrophoretic mobility shift assays and size exclusion chromatography. Further, heterologous expression of BR187–378 or the longer BR120–378 construct on the surface of a Gram-positive model host bacterium resulted in the formation of cellular aggregates that was significantly enhanced in the presence of DNA. Crystal structure analyses revealed the formation of BR187–385 homo-dimers via an intermolecular β-sheet, resulting in a positively charged concave surface, shaped to accommodate the acidic helical DNA structure. Furthermore, small angle X-ray scattering and circular dichroism studies indicate that the aggregate-enhancing N-terminal region of BR120–166 adopts an extended, non-globular structure. Altogether, our results suggest that PsrP adheres to extracellular DNA in the biofilm matrix and thus promotes pneumococcal biofilm formation. PMID:27582320

  19. Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes.

    PubMed Central

    Schramm, A; Larsen, L H; Revsbech, N P; Ramsing, N B; Amann, R; Schleifer, K H

    1996-01-01

    Microprofiles of O2 and NO3- were measured in nitrifying biofilms from the trickling filter of an aquaculture water recirculation system. By use of a newly developed biosensor for NO3-, it was possible to avoid conventional interference from other ions. Nitrification was restricted to a narrow zone of 50 microns on the very top of the film. In the same biofilms, the vertical distributions of members of the lithoautotrophic ammonia-oxidizing genus Nitrosomonas and of the nitrite-oxidizing genus Nitrobacter were investigated by applying fluorescence in situ hybridization of whole fixed cells with 16S rRNA-targeted oligonucleotide probes in combination with confocal laser-scanning microscopy. Ammonia oxidizers formed a dense layer of cell clusters in the upper part of the biofilm, whereas the nitrite oxidizers showed less-dense aggregates in close vicinity to the Nitrosomonas clusters. Both species were not restricted to the oxic zone of the biofilm but were also detected in substantially lower numbers in the anoxic layers and even occasionally at the bottom of the biofilm. PMID:8953735

  20. Establishment and Early Succession of Bacterial Communities in Monochloramine-Treated Drinking Water Biofilms

    EPA Science Inventory

    Monochloramine is increasingly used as a drinking water disinfectant because it forms lower levels of regulated disinfection by-products. While its use has been shown to increase nitrifying bacteria, little is known about the bacterial succession within biofilms in monochloramin...

  1. Establishment and Early Succession of Bacterial Communities in Monochloramine-Treated Drinking Water Biofilms

    EPA Science Inventory

    Monochloramine is increasingly used as a drinking water disinfectant because it forms lower levels of regulated disinfection by-products. While its use has been shown to increase nitrifying bacteria, little is known about the bacterial succession within biofilms in monochloramin...

  2. Protein aggregation as an antibiotic design strategy.

    PubMed

    Bednarska, Natalia G; van Eldere, Johan; Gallardo, Rodrigo; Ganesan, Ashok; Ramakers, Meine; Vogel, Isabel; Baatsen, Pieter; Staes, An; Goethals, Marc; Hammarström, Per; Nilsson, K Peter R; Gevaert, Kris; Schymkowitz, Joost; Rousseau, Frederic

    2016-03-01

    Taking advantage of the xenobiotic nature of bacterial infections, we tested whether the cytotoxicity of protein aggregation can be targeted to bacterial pathogens without affecting their mammalian hosts. In particular, we examined if peptides encoding aggregation-prone sequence segments of bacterial proteins can display antimicrobial activity by initiating toxic protein aggregation in bacteria, but not in mammalian cells. Unbiased in vitro screening of aggregating peptide sequences from bacterial genomes lead to the identification of several peptides that are strongly bactericidal against methicillin-resistant Staphylococcus aureus. Upon parenteral administration in vivo, the peptides cured mice from bacterial sepsis without apparent toxic side effects as judged from histological and hematological evaluation. We found that the peptides enter and accumulate in the bacterial cytosol where they cause aggregation of bacterial polypeptides. Although the precise chain of events that leads to cell death remains to be elucidated, the ability to tap into aggregation-prone sequences of bacterial proteomes to elicit antimicrobial activity represents a rich and unexplored chemical space to be mined in search of novel therapeutic strategies to fight infectious diseases. © 2015 John Wiley & Sons Ltd.

  3. Interaction of operational and physicochemical factors leading to Gordonia amarae-like foaming in an incompletely nitrifying activated sludge plant.

    PubMed

    Asvapathanagul, Pitiporn; Huang, Zhonghua; Gedalanga, Phillip B; Baylor, Amber; Olson, Betty H

    2012-12-01

    The overgrowth of Gordonia amarae-like bacteria in the mixed liquor of an incompletely nitrifying water reclamation plant was inversely correlated with temperature (r = -0.78; P < 0.005) and positively correlated with the solids retention time (SRT) obtained a week prior to sampling (r = 0.67; P < 0.005). Drops followed by spikes in the food-to-mass ratio (0.18 to 0.52) and biochemical oxygen demand concentrations in primary effluent (94 to 298 mg liter(-1)) occurred at the initiation of G. amarae-like bacterial growth. The total bacterial concentration did not increase as concentrations of G. amarae-like cells increased, but total bacterial cell concentrations fluctuated in a manner similar to that of G. amarae-like bacteria in the pseudo-steady state. The ammonium ion removal rate (percent) was inversely related to G. amarae-like cell concentrations during accelerated growth and washout phases. The dissolved oxygen concentration decreased as the G. amarae-like cell concentration decreased. The concentrations of G. amarae-like cells peaked (2.47 × 10(9) cells liter(-1)) approximately 1.5 months prior to foaming. Foaming occurred during the late pseudo-steady-state phase, when temperature declines reversed. These findings suggested that temperature changes triggered operational and physicochemical changes favorable to the growth of G. amarae-like bacteria. Fine-scale quantitative PCR (qPCR) monitoring at weekly intervals allowed a better understanding of the factors affecting this organism and indicated that frequent sampling was required to obtain statistical significance with factors changing as the concentrations of this organism increased. Furthermore, the early identification of G. amarae-like cells when they are confined to mixed liquor (10(7) cells liter(-1)) allows management strategies to prevent foaming.

  4. Interaction of Operational and Physicochemical Factors Leading to Gordonia amarae-Like Foaming in an Incompletely Nitrifying Activated Sludge Plant

    PubMed Central

    Asvapathanagul, Pitiporn; Huang, Zhonghua; Gedalanga, Phillip B.; Baylor, Amber

    2012-01-01

    The overgrowth of Gordonia amarae-like bacteria in the mixed liquor of an incompletely nitrifying water reclamation plant was inversely correlated with temperature (r = −0.78; P < 0.005) and positively correlated with the solids retention time (SRT) obtained a week prior to sampling (r = 0.67; P < 0.005). Drops followed by spikes in the food-to-mass ratio (0.18 to 0.52) and biochemical oxygen demand concentrations in primary effluent (94 to 298 mg liter−1) occurred at the initiation of G. amarae-like bacterial growth. The total bacterial concentration did not increase as concentrations of G. amarae-like cells increased, but total bacterial cell concentrations fluctuated in a manner similar to that of G. amarae-like bacteria in the pseudo-steady state. The ammonium ion removal rate (percent) was inversely related to G. amarae-like cell concentrations during accelerated growth and washout phases. The dissolved oxygen concentration decreased as the G. amarae-like cell concentration decreased. The concentrations of G. amarae-like cells peaked (2.47 × 109 cells liter−1) approximately 1.5 months prior to foaming. Foaming occurred during the late pseudo-steady-state phase, when temperature declines reversed. These findings suggested that temperature changes triggered operational and physicochemical changes favorable to the growth of G. amarae-like bacteria. Fine-scale quantitative PCR (qPCR) monitoring at weekly intervals allowed a better understanding of the factors affecting this organism and indicated that frequent sampling was required to obtain statistical significance with factors changing as the concentrations of this organism increased. Furthermore, the early identification of G. amarae-like cells when they are confined to mixed liquor (107 cells liter−1) allows management strategies to prevent foaming. PMID:22983974

  5. Effect of two broad-spectrum antibiotics on activity and stability of continuous nitrifying system.

    PubMed

    Campos, J L; Garrido, J M; Méndez, R; Lema, J M

    2001-07-01

    The effects of two broad-spectrum antibiotics, chloramphenicol and oxytetracycline hydrochloride, on the microbial activity and biofilm stability of a mixed nitrifying culture were studied. These antibiotics are present in some wastewaters generated in cattle farms or pharmaceutical industries. A 1-L fermentor, in which nitrifiers grew both in suspension and in a biofilm, was used during the experiments. Chloramphenicol (10-250 mg/L) barely had any effect on biofilm stability and nitrification. Ammonia was fully oxidized to nitrate. However, oxytetracycline caused biofilm sloughing at concentrations of 10 mg/L, but nitrification was not inhibited at antibiotic concentrations up to 100 mg/L. When the concentration of oxytetracycline chlorohydrate was increased stepwise from 100 to 250 mg/L, nitrification was inhibited by 50%. The dissolved organic carbon measurements in both the influent and effluent showed that the antibiotics were neither mineralized by the mixed nitrifying culture nor accumulated in the system. Furthermore, the microbial tests did not reveal the presence of active antibiotics in the effluent. This fact indicates that both cloramphenicol and oxytetracycline were degraded by the nitrifying sludge but not mineralized.

  6. Transcriptional and physiological responses of nitrifying bacteria to heavy metal inhibition

    EPA Science Inventory

    Heavy metals have been shown to inhibit nitrification, a key process in the removal of nitrogen in wastewater treatment plants. In the present study, the effects of nickel, zinc, lead and cadmium on nitrifying enrichment cultures were studied in batch reactors. The transcriptiona...

  7. Transcriptional and physiological responses of nitrifying bacteria to heavy metal inhibition

    EPA Science Inventory

    Heavy metals have been shown to inhibit nitrification, a key process in the removal of nitrogen in wastewater treatment plants. In the present study, the effects of nickel, zinc, lead and cadmium on nitrifying enrichment cultures were studied in batch reactors. The transcriptiona...

  8. A sensitive crude oil bioassay indicates that oil spills potentially induce a change of major nitrifying prokaryotes from the archaea to the bacteria.

    PubMed

    Urakawa, Hidetoshi; Garcia, Juan C; Barreto, Patricia D; Molina, Gabriela A; Barreto, Jose C

    2012-05-01

    The sensitivity of nitrifiers to crude oil released by the BP Deepwater Horizon oil spill in Gulf of Mexico was examined using characterized ammonia-oxidizing bacteria and archaea to develop a bioassay and to gain further insight into the ecological response of these two groups of microorganisms to marine oil spills. Inhibition of nitrite production was observed among all the tested ammonia-oxidizing organisms at 100 ppb crude oil. Nitrosopumilus maritimus, a cultured representative of the abundant Marine Group I Archaea, showed 20% inhibition at 1 ppb, a much greater degree of sensitivity to petroleum than the tested ammonia-oxidizing and heterotrophic bacteria. The differing susceptibility may have ecological significance since a shift to bacterial dominance in response to an oil spill could potentially persist and alter trophic interactions influenced by availability of different nitrogen species.

  9. Long term assessment of factors affecting nitrifying bacteria communities and N-removal in a full-scale biological process treating high strength hazardous wastewater.

    PubMed

    Kim, Young Mo; Park, Hongkeun; Cho, Kyung Hwa; Park, Jong Moon

    2013-04-01

    Over a 3 year period, interactions between nitrifying bacterial communities and the operational parameters of a full-scale wastewater treatment plant were analyzed to assess their impact on nitrification performance. Throughout the study period, nitrification fluctuated while Nitrosomonas europaea and Nitrosomonas nitrosa, the two major ammonia oxidizing bacteria (AOB) communities, showed resistance to changes in operational and environmental conditions. Nitrobacter populations mostly exceeded those of Nitrospira within nitrite oxidizing bacteria (NOB). Meanwhile, principal component analysis (PCA) results revealed that a close association between Nitrobacter and nitrite concentration as well as a direct correlation between the quantity of AOB and influent SCN- concentration. The serial shifts of data points over time showed that the nitrification of a full-scale treatment plant has been gradually suppressed by the influence of influent COD and phenol concentrations.

  10. Application of a novel functional gene microarray to probe the functional ecology of ammonia oxidation in nitrifying activated sludge.

    PubMed

    Short, Michael D; Abell, Guy C J; Bodrossy, Levente; van den Akker, Ben

    2013-01-01

    We report on the first study trialling a newly-developed, functional gene microarray (FGA) for characterising bacterial and archaeal ammonia oxidisers in activated sludge. Mixed liquor (ML) and media biofilm samples from a full-scale integrated fixed-film activated sludge (IFAS) plant were analysed with the FGA to profile the diversity and relative abundance of ammonia-oxidising archaea and bacteria (AOA and AOB respectively). FGA analyses of AOA and AOB communities revealed ubiquitous distribution of AOA across all samples - an important finding for these newly-discovered and poorly characterised organisms. Results also revealed striking differences in the functional ecology of attached versus suspended communities within the IFAS reactor. Quantitative assessment of AOB and AOA functional gene abundance revealed a dominance of AOB in the ML and approximately equal distribution of AOA and AOB in the media-attached biofilm. Subsequent correlations of functional gene abundance data with key water quality parameters suggested an important functional role for media-attached AOB in particular for IFAS reactor nitrification performance and indicate possible functional redundancy in some IFAS ammonia oxidiser communities. Results from this investigation demonstrate the capacity of the FGA to resolve subtle ecological shifts in key microbial communities in nitrifying activated sludge and indicate its value as a tool for better understanding the linkages between the ecology and performance of these engineered systems.

  11. Application of a Novel Functional Gene Microarray to Probe the Functional Ecology of Ammonia Oxidation in Nitrifying Activated Sludge

    PubMed Central

    Short, Michael D.; Abell, Guy C. J.; Bodrossy, Levente; van den Akker, Ben

    2013-01-01

    We report on the first study trialling a newly-developed, functional gene microarray (FGA) for characterising bacterial and archaeal ammonia oxidisers in activated sludge. Mixed liquor (ML) and media biofilm samples from a full-scale integrated fixed-film activated sludge (IFAS) plant were analysed with the FGA to profile the diversity and relative abundance of ammonia-oxidising archaea and bacteria (AOA and AOB respectively). FGA analyses of AOA and AOB communities revealed ubiquitous distribution of AOA across all samples – an important finding for these newly-discovered and poorly characterised organisms. Results also revealed striking differences in the functional ecology of attached versus suspended communities within the IFAS reactor. Quantitative assessment of AOB and AOA functional gene abundance revealed a dominance of AOB in the ML and approximately equal distribution of AOA and AOB in the media-attached biofilm. Subsequent correlations of functional gene abundance data with key water quality parameters suggested an important functional role for media-attached AOB in particular for IFAS reactor nitrification performance and indicate possible functional redundancy in some IFAS ammonia oxidiser communities. Results from this investigation demonstrate the capacity of the FGA to resolve subtle ecological shifts in key microbial communities in nitrifying activated sludge and indicate its value as a tool for better understanding the linkages between the ecology and performance of these engineered systems. PMID:24155925

  12. Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Continuously Percolated Soil Columns

    PubMed Central

    Verhagen, Frank J. M.; Duyts, Hendrik; Laanbroek, Hendrikus J.

    1992-01-01

    Although the absence of nitrate formation in grassland soils rich in organic matter has often been reported, low numbers of nitrifying bacteria are still found in these soils. To obtain more insight into these observations, we studied the competition for limiting amounts of ammonium between the chemolithotrophic ammonium-oxidizing species Nitrosomonas europaea and the heterotrophic species Arthrobacter globiformis in the presence of Nitrobacter winogradskyi with soil columns containing calcareous sandy soil. The soil columns were percolated continuously at a dilution rate of 0.007 h-1, based on liquid volumes, with medium containing 5 mM ammonium and different amounts of glucose ranging from 0 to 12 mM.A. globiformis was the most competitive organism for limiting amounts of ammonium. The numbers of N. europaea and N. winogradskyi cells were lower at higher glucose concentrations, and the potential ammonium-oxidizing activities in the uppermost 3 cm of the soil columns were nonexistent when at least 10 mM glucose was present in the reservoir, although 107 nitrifying cells per g of dry soil were still present. This result demonstrated that there was no correlation between the numbers of nitrifying bacteria and their activities. The numbers and activities of N. winogradskyi cells decreased less than those of N. europaea cells in all layers of the soil columns, probably because of heterotrophic growth of the nitrite-oxidizing bacteria on organic substrates excreted by the heterotrophic bacteria or because of nitrate reduction at reduced oxygen concentrations by the nitrite-oxidizing bacteria. Our conclusion was that the nitrifying bacteria were less competitive than the heterotrophic bacteria for ammonium in soil columns but that they survived as viable inactive cells. Inactive nitrifying bacteria may also be found in the rhizosphere of grassland plants, which is rich in organic carbon. They are possibly reactivated during periods of net mineralization. PMID:16348787

  13. Bacterial leakage of mineral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and Super-EBA as a root-end filling material.

    PubMed

    Fischer, E J; Arens, D E; Miller, C H

    1998-03-01

    Several dye leakage studies have demonstrated the fact that mineral trioxide aggregate (MTA) leaks significantly less than other root-end filling materials. The purpose of this study was to determine the time needed for Serratia marcescens to penetrate a 3 mm thickness of zinc-free amalgam, Intermediate Restorative Material (IRM), Super-EBA, and MTA when these materials were used as root-end filling materials. Fifty-six, single-rooted extracted human teeth were cleaned and shaped with a series of .04 Taper rotary instruments (Pro-series 29 files). Once the canals were prepared in a crown down approach, the ends were resected and 48 root-end cavities were ultrasonically prepared to a 3 mm depth. The teeth were then steam sterilized. Using an aseptic technique, under a laminar air flow hood, the root-end cavities were filled with amalgam, IRM, Super-EBA, and MTA. Four root-end cavities were filled with thermoplasticized gutta-percha without a root canal sealer and served as positive controls. Another four root-end cavities were filled with sticky wax covered with two layers of nail polish and served as negative controls. The teeth were attached to presterilized (ethylene oxide gas) plastic caps, and the root ends were placed into 12-ml vials of phenol red broth. Using a micropipette, a tenth of a milliliter of S. marcescens was placed into the root canal of each tooth. To test the sterility of the apparatus set-up, the root canals of two teeth with test root-end filling materials and one tooth from the positive and negative control groups were filled with sterile saline. The number of days required for S. marcescens to penetrate the four root-end filling materials and grow in the phenol red broth was recorded and analyzed. Most of the samples filled with zinc-free amalgam leaked bacteria in 10 to 63 days. IRM began leaking 28 to 91 days. Super-EBA began leaking 42 to 101 days. MTA did not begin leaking until day 49. At the end of the study, four of the MTA samples

  14. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  15. Exploration of three heterotrophic nitrifying strains from a tilapia pond for their characteristics of inorganic nitrogen use and application in aquaculture water.

    PubMed

    Fan, Limin; Chen, Jiazhang; Liu, Qi; Wu, Wei; Meng, Shunlong; Song, Chao; Qu, Jianhong; Xu, Pao

    2015-03-01

    Three heterotrophic nitrifying bacterial strains, HLf01, HBf01 and HHf01, were isolated from a pond where genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) was intensively cultured during the annual peak breeding period. Analysis of biochemical, morphological characteristics and sequences analysis of 16S rDNA identified strains HLf01 and HBf01 as Pseudomonas sp., and strain HHf01 as Acinetobacter baumannii. Further analysis of heterotrophic nitrifying medium inorganic nitrogen used showed that most of the ammonia nitrogen was removed after 48 h. Strains HBf01 and HHf01 removed 67.9% and 76.7% of the total ammonia nitrogen after 24 h, recording the mass ratio of carbon to nitrogen used as 10.6 to 1 and 11.7 to 1, respectively. Strain HLf01 used a C:N ratio of 22.7 to 1 with a total of 43.8% ammonia nitrogen removed. In denitrifying media, strains HBf01 and HHf01 may have used nitrate and nitrite as the sole nitrogen source by strain HLf01. Generally, all the three strains used nitrogen in the order ammonia > nitrite > nitrate when all the three nitrogen forms were recorded present. Although the bacterial strains consumed dissolved organic carbon, it was limited when ammonia was the main source of nitrogen compared with other forms of inorganic nitrogen. Also, the test of the three strains on aquaculture water showed similar results of efficiency of ammonia nitrogen removal with the test of inorganic nitrogen use. Copyright © 2014. Published by Elsevier B.V.

  16. Ralstonia insidiosa induces cell aggregation by Listeria monocytogenes

    USDA-ARS?s Scientific Manuscript database

    Biofilm formation is an important strategy for foodborne bacterial pathogens to survive in stressful environments such as fresh produce processing facilities. Bacterial cell aggregation strongly promotes the initiation of microcolonies and the formation of biofilms on abiological surfaces. We previ...

  17. Kinetic parameters for 17alpha-ethinylestradiol removal by nitrifying activated sludge developed in a membrane bioreactor.

    PubMed

    Clouzot, L; Doumenq, P; Roche, N; Marrot, B

    2010-08-01

    The synthetic hormone 17alpha-ethinylestradiol (EE2) is primarily removed in wastewater treatment plants (WWTPs) by sorption, and nitrifying biomass has been shown to be responsible for EE2 biodegradation. Membrane bioreactor (MBR) technology was chosen to develop a community of autotrophic, nitrifying micro-organisms and determine kinetic parameters for EE2 biodegradation. Biological inhibition by azide was applied to differentiate sorption from biodegradation. Activated sludge (AS) was acclimated in the MBR to a substrate specific to autotrophic biomass and resulted in an increase in nitrifying activity. Acclimated AS was used to successfully biodegrade EE2 (11% increase in EE2 removal), and the overall removal of EE2 was determined to be 99% (sorption+biodegradation). AS used directly from a WWTP without acclimation removed EE2 only through sorption (88% removal of EE2). Therefore, higher nitrifying activity developed by acclimating AS allowed almost complete removal of EE2. Copyright 2010 Elsevier Ltd. All rights reserved.

  18. Co-cultivation of microalgae and nitrifiers for higher biomass production and better carbon capture.

    PubMed

    Bilanovic, Dragoljub; Holland, Mark; Starosvetsky, Jeanna; Armon, Robert

    2016-11-01

    The aim of this work was to study co-cultivation of nitrifiers with microalgae as a non-intrusive technique for selective removal of oxygen generated by microalgae. Biomass concentration was, at least, 23% higher in mixed-cultures where nitrifiers kept the dissolved oxygen concentration below 9.0μLL(-1) than in control Chlorella vulgaris axenic-cultures where the concentration of dissolved oxygen was higher than 10.0μLL(-1). This approach to eliminating oxygen inhibition of microalgal growth could become the basis for the development of advanced microalgae reactors for removal of CO2 from the atmosphere, and concentrated CO2 streams. CO2 sequestration would become a chemically and geologically safer and environmentally more sound technology provided it uses microalgal, or other biomass, instead of CO2, for carbon storage.

  19. Nitrifying microorganisms in fixed-bed biofilm reactors fed with different nitrite and ammonia concentrations.

    PubMed

    ter Haseborg, Eike; Zamora, Talia Mateu; Fröhlich, Jörn; Frimmel, Fritz H

    2010-03-01

    Nitrifying bacteria and archaea were fed in fixed-bed biofilm reactors with different nitrite and ammonia concentrations in synthetic and real wastewater. During high nitrite concentrations (rho(NO(2)(-))=5-10mg/L), an increase in the abundance of Nitrobacter species was detected with fluorescence in situ hybridization (FISH), while Nitrospira species disappeared to a large extent. During high ammonia concentrations (rho(NH(4)(+))=60-80 mg/L), a slight increase in ammonia-oxidizing bacteria was obtained, while the abundance of archaebacteria remained unchanged. Lab-scale reactors showed a similar nitrifying microbial population as reactors fed with real wastewater. However, increased abundances of Nitrospira species as observed in wastewater reactors and in the wastewater trickling filters could not be found in the laboratory reactors. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  20. Two-step nitrification in a pure moving bed biofilm reactor-membrane bioreactor for wastewater treatment: nitrifying and denitrifying microbial populations and kinetic modeling.

    PubMed

    Leyva-Díaz, J C; González-Martínez, A; Muñío, M M; Poyatos, J M

    2015-12-01

    The moving bed biofilm reactor-membrane bioreactor (MBBR-MBR) is a novel solution to conventional activated sludge processes and membrane bioreactors. In this study, a pure MBBR-MBR was studied. The pure MBBR-MBR mainly had attached biomass. The bioreactor operated with a hydraulic retention time (HRT) of 9.5 h. The kinetic parameters for heterotrophic and autotrophic biomasses, mainly nitrite-oxidizing bacteria (NOB), were evaluated. The analysis of the bacterial community structure of the ammonium-oxidizing bacteria (AOB), NOB, and denitrifying bacteria (DeNB) from the pure MBBR-MBR was carried out by means of pyrosequencing to detect and quantify the contribution of the nitrifying and denitrifying bacteria in the total bacterial community. The relative abundance of AOB, NOB, and DeNB were 5, 1, and 3%, respectively, in the mixed liquor suspended solids (MLSS), and these percentages were 18, 5, and 2%, respectively, in the biofilm density (BD) attached to carriers. The pure MBBR-MBR had a high efficiency of total nitrogen (TN) removal of 71.81±16.04%, which could reside in the different bacterial assemblages in the fixed biofilm on the carriers. In this regard, the kinetic parameters for autotrophic biomass had values of YA=2.3465 mg O2 mg N(-1), μm, A=0.7169 h(-1), and KNH=2.0748 mg NL(-1).

  1. Chronic impact of tetracycline on nitrification kinetics and the activity of enriched nitrifying microbial culture.

    PubMed

    Katipoglu-Yazan, Tugce; Merlin, Christophe; Pons, Marie-Noëlle; Ubay-Cokgor, Emine; Orhon, Derin

    2015-04-01

    This study evaluated the chronic impact of tetracycline on biomass with enriched nitrifying community sustained in a lab-scale activated sludge system. For this purpose, a fill and draw reactor fed with 100 mg COD/L of peptone mixture and 50 mg N/L of ammonia was sustained at a sludge age of 15 days. At steady-state, the reactor operation was continued with a daily tetracycline dosing of 50 mg/L for more than 40 days, with periodic monitoring of the microbial composition, the nitrifying bacteria abundance, as well as the amoA and 16S rRNA gene activity, using molecular techniques. Changes in the kinetics of nitrification were quantified by modelling concentration profiles of major nitrogen fractions and oxygen uptake rate profiles derived from parallel batch experiments. Activated sludge modeling results indicated inhibitory impact of tetracycline on the growth of nitrifiers with a significant increase of the half saturation coefficients in corresponding rate equations. Tetracycline also inactivated biomass components of the enriched culture at a gradually increasing rate with time of exposure, leading to total collapse of nitrification. Molecular analyses revealed significant changes in the composition of the microbial community throughout the observation period. They also showed that continuous exposure to tetracycline inflicted significant reduction in amoA mRNA and 16S rRNA levels directly affecting nitrification. The chronic impact was much more pronounced on the ammonia oxidizing bacteria (AOB) community. These observations explained the basis of numerical changes identified in the growth kinetics of nitrifiers under stress conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Clinoptilolite: a possible support material for nitrifying biofilms for effective control of ammonium effluent quality?

    PubMed

    Inan, H; Beler Baykal, B

    2005-01-01

    Ammonium selective natural zeolite clinoptilolite is suggested as a possible support material for nitrifying biofilms to help improve effluent ammonium quality through its high capacity of ammonium removal in the process of ion exchange. This will especially be helpful in cases where the biofilter receives peak or variable loads routinely or occasionally. At the time of peak loads or shocks of ammonium, ion exchange capacity will provide a buffer for the effluent ammonium quality. Data to support this suggestion is presented.

  3. Biological removal of the xenobiotic trichloroethylene (TCE) through cometabolism in nitrifying systems.

    PubMed

    Kocamemi, B Alpaslan; Ceçen, F

    2010-01-01

    In the present study, cometabolic TCE degradation was evaluated using NH(4)-N as the growth-substrate. At initial TCE concentrations up to 845 microg/L, TCE degradation followed first-order kinetics. The increase in ammonium utilization rate favored the degradation of TCE. This ensured that biological transformation of TCE in nitrifying systems is accomplished through a cometabolic pathway by the catalysis of non-specific ammonia oxygenase enzyme of nitrifiers. The transformation yield (T(y)) of TCE, the amount of TCE degraded per unit mass of NH(4)-N, strongly depended on the initial NH(4)-N and TCE concentrations. In order to allow a rough estimation of TCE removal and nitrification at different influent TCE and NH(4)-N concentrations, a linear relationship was developed between 1/T(y) and the initial NH(4)-N/TCE ratio. The estimated T(y) values lead to the conclusion that nitrifying systems are promising candidates for biological removal of TCE through cometabolism.

  4. Hydroxylamine diffusion can enhance N₂O emissions in nitrifying biofilms: a modeling study.

    PubMed

    Sabba, Fabrizio; Picioreanu, Cristian; Pérez, Julio; Nerenberg, Robert

    2015-02-03

    Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas. However, little is known about N2O emissions from biofilm processes. We adapted an existing suspended-growth mathematical model to explore N2O emissions from nitrifying biofilms. The model included N2O formation by ammonia-oxidizing bacteria (AOB) via the hydroxylamine and the nitrifier denitrification pathways. Our model suggested that N2O emissions from nitrifying biofilms could be significantly greater than from suspended growth systems under similar conditions. The main cause was the formation and diffusion of hydroxylamine, an AOB nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. In the anoxic regions, hydroxylamine oxidation by AOB provided reducing equivalents used solely for nitrite reduction to N2O, since there was no competition with oxygen. For a continuous system, very high and very low dissolved oxygen (DO) concentrations resulted in lower emissions, while intermediate values led to higher emissions. Higher bulk ammonia concentrations and greater biofilm thicknesses increased emissions. The model effectively predicted N2O emissions from an actual pilot-scale granular sludge reactor for sidestream nitritation, but significantly underestimated the emissions when the NH2OH diffusion coefficient was assumed to be minimal. This numerical study suggests an unexpected and important role of hydroxylamine in N2O emission in biofilms.

  5. Impact of cell cluster size on apparent half-saturation coefficients for oxygen in nitrifying sludge and biofilms.

    PubMed

    Picioreanu, Cristian; Pérez, Julio; van Loosdrecht, Mark C M

    2016-12-01

    A three-dimensional (3-D) diffusion-reaction model was used to assess the effects of nitrifiers growing in cell clusters on the apparent oxygen half-saturation coefficients in activated sludge flocs. The model allows conciliation of seemingly contradictory reports by several research groups. Although intrinsic half-saturation coefficients (i.e., not affected by diffusion) show a better affinity for oxygen for ammonia oxidizing (AOB) than for nitrite oxidizing bacteria (NOB) (KO,AOB < KO,NOB), measurements in flocs often produced reversed apparent values (KO,AOB,app > KO,NOB,app), which can now be explained by the 3-D model with AOB and NOB microcolonies. This effect cannot be described with a conventional 1-D homogeneous model because the reversion of the AOB/NOB apparent KO is caused by the high biomass density and resulting concentration gradients inside the microcolonies. Two main factors explain the reversion of the half-saturation coefficients: the difference in oxygen yields (for NOB lower than for AOB) and the difference in colony size (NOB colonies are smaller than those of AOB). The strongest increase in the apparent half-saturation coefficients is linked to the colony size, rather than to the floc size. For high-density microbial aggregates (i.e., granular sludge), the need for a stratified population (AOB outer shell, NOB inner layers) was revealed in order to outcompete NOB. This study stresses the need for a more detailed description of the biomass distribution in activated sludge, granular sludge and biofilm reactors when elucidating the mechanisms for NOB repression.

  6. Assessment of bacterial and structural dynamics in aerobic granular biofilms.

    PubMed

    Weissbrodt, David G; Neu, Thomas R; Kuhlicke, Ute; Rappaz, Yoan; Holliger, Christof

    2013-01-01

    Aerobic granular sludge (AGS) is based on self-granulated flocs forming mobile biofilms with a gel-like consistence. Bacterial and structural dynamics from flocs to granules were followed in anaerobic-aerobic sequencing batch reactors (SBR) fed with synthetic wastewater, namely a bubble column (BC-SBR) operated under wash-out conditions for fast granulation, and two stirred-tank enrichments of Accumulibacter (PAO-SBR) and Competibacter (GAO-SBR) operated at steady-state. In the BC-SBR, granules formed within 2 weeks by swelling of Zoogloea colonies around flocs, developing subsequently smooth zoogloeal biofilms. However, Zoogloea predominance (37-79%) led to deteriorated nutrient removal during the first months of reactor operation. Upon maturation, improved nitrification (80-100%), nitrogen removal (43-83%), and high but unstable dephosphatation (75-100%) were obtained. Proliferation of dense clusters of nitrifiers, Accumulibacter, and Competibacter from granule cores outwards resulted in heterogeneous bioaggregates, inside which only low abundance Zoogloea (<5%) were detected in biofilm interstices. The presence of different extracellular glycoconjugates detected by fluorescence lectin-binding analysis showed the complex nature of the intracellular matrix of these granules. In the PAO-SBR, granulation occurred within two months with abundant and active Accumulibacter populations (56 ± 10%) that were selected under full anaerobic uptake of volatile fatty acids and that aggregated as dense clusters within heterogeneous granules. Flocs self-granulated in the GAO-SBR after 480 days during a period of over-aeration caused by biofilm growth on the oxygen sensor. Granules were dominated by heterogeneous clusters of Competibacter (37 ± 11%). Zoogloea were never abundant in biomass of both PAO- and GAO-SBRs. This study showed that Zoogloea, Accumulibacter, and Competibacter affiliates can form granules, and that the granulation mechanisms rely on the dominant population

  7. Assessment of bacterial and structural dynamics in aerobic granular biofilms

    PubMed Central

    Weissbrodt, David G.; Neu, Thomas R.; Kuhlicke, Ute; Rappaz, Yoan; Holliger, Christof

    2013-01-01

    Aerobic granular sludge (AGS) is based on self-granulated flocs forming mobile biofilms with a gel-like consistence. Bacterial and structural dynamics from flocs to granules were followed in anaerobic-aerobic sequencing batch reactors (SBR) fed with synthetic wastewater, namely a bubble column (BC-SBR) operated under wash-out conditions for fast granulation, and two stirred-tank enrichments of Accumulibacter (PAO-SBR) and Competibacter (GAO-SBR) operated at steady-state. In the BC-SBR, granules formed within 2 weeks by swelling of Zoogloea colonies around flocs, developing subsequently smooth zoogloeal biofilms. However, Zoogloea predominance (37–79%) led to deteriorated nutrient removal during the first months of reactor operation. Upon maturation, improved nitrification (80–100%), nitrogen removal (43–83%), and high but unstable dephosphatation (75–100%) were obtained. Proliferation of dense clusters of nitrifiers, Accumulibacter, and Competibacter from granule cores outwards resulted in heterogeneous bioaggregates, inside which only low abundance Zoogloea (<5%) were detected in biofilm interstices. The presence of different extracellular glycoconjugates detected by fluorescence lectin-binding analysis showed the complex nature of the intracellular matrix of these granules. In the PAO-SBR, granulation occurred within two months with abundant and active Accumulibacter populations (56 ± 10%) that were selected under full anaerobic uptake of volatile fatty acids and that aggregated as dense clusters within heterogeneous granules. Flocs self-granulated in the GAO-SBR after 480 days during a period of over-aeration caused by biofilm growth on the oxygen sensor. Granules were dominated by heterogeneous clusters of Competibacter (37 ± 11%). Zoogloea were never abundant in biomass of both PAO- and GAO-SBRs. This study showed that Zoogloea, Accumulibacter, and Competibacter affiliates can form granules, and that the granulation mechanisms rely on the dominant

  8. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  9. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  10. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  11. Development of Denitrifying and Nitrifying Bacteria and Their Co-occurrence in Newly Created Biofilms in Urban Streams

    NASA Astrophysics Data System (ADS)

    Vaessen, T. N.; Martí Roca, E.; Pinay, G.; Merbt, S. N.

    2015-12-01

    Biofilms play a pivotal role on nutrient cycling in streams, which ultimately dictates the export of nutrients to downstream ecosystems. The extent to which biofilms influence the concentration of dissolved nutrients, oxygen and pH in the water column may be determined by the composition of the microbial assemblages and their activity. Evidence of biological interactions among bacteria and algae are well documented. However, the development, succession and co-occurence of nitrifying and denitrifying bacteria remain poorly understood. These bacteria play a relevant role on the biogeochemical process associated to N cycling, and their relative abundance can dictate the fate of dissolved inorganic nitrogen in streams. In particular, previous studies indicated that nitrifiers are enhanced in streams receiving inputs from wastewater treatment plant (WWTP) effluents due to both increases in ammonium concentration and inputs of nitrifiers. However, less is known about the development of denitrifiers in receiving streams, although environmental conditions seem to favor it. We conducted an in situ colonization experiment in a stream receiving effluent from a WWTP to examine how this input influences the development and co-occurrence of nitrifying and denitrifying bacteria. We placed artificial substrata at different locations relative to the effluent and sampled them over time to characterize the developed biofilm in terms of bulk measurements (organic matter content and algae) as well as in terms of abundance of nitrifiers and denitrifiers (using qPCR). The results of this study contribute to a better understanding of the temporal dynamics of denitrifiers and nitrifiers in relation to the developed organic matter, dissolved oxygen and pH and the biomass accrual in stream biofilms under the influence of nutrients inputs from WWTP effluent. Ultimately, the results provide insights on the potential role of nitrifiers and denitrifiers on N cycling in WWTP effluent receiving

  12. Marine bacterial degradation of brominated methanes

    USGS Publications Warehouse

    Goodwin, K.D.; Lidstrom, M.E.; Oremland, R.S.

    1997-01-01

    Brominated methanes are ozone-depleting compounds whose natural sources include marine algae such as kelp. Brominated methane degradation by bacteria was investigated to address whether bacterial processes might effect net emission of these compounds to the atmosphere. Bacteria in seawater collected from California kelp beds degraded CH2Br2 but not CHBr3. Specific inhibitors showed that methanotrophs and nitrifiers did not significantly contribute to CH2Br2 removal. A seawater enrichment culture oxidized 14CH2Br2 to 14CO2 as well as 14CH3Br to 14CO2. The rates of CH2Br2 degradation in laboratory experiments suggest that bacterial degradation of CH2Br2 in a kelp bed accounts for <1% of the CH2Br2 produced by the kelp. However, the half-life of CH2Br2 due to bacterial removal appears faster than hydrolysis and within an order of magnitude of volatilization to the atmosphere.Brominated methanes are ozone-depleting compounds whose natural sources include marine algae such as kelp. Brominated methane degradation by bacteria was investigated to address whether bacterial processes might effect net emission of these compounds to the atmosphere. Bacteria in seawater collected from California kelp beds degraded CH2Br2 but not CHBr3. Specific inhibitors showed that methanotrophs and nitrifiers did not significantly contribute to CH2Br2 removal. A seawater enrichment culture oxidized 14CH2Br2 to 14CO2 as well as 14CH3Br to 14CO2. The rates of CH2Br2 degradation in laboratory experiments suggest that bacterial degradation of CH2Br2 in a kelp bed accounts for <1% of the CH2Br2 produced by the kelp. However, the half-life of CH2Br2 due to bacterial removal appears faster than hydrolysis and within an order of magnitude of volatilization to the atmosphere.

  13. Variability of nitrifying communities in surface coastal waters of the Eastern South Pacific (∼36° S).

    PubMed

    Levipan, Héctor A; Molina, Verónica; Anguita, Cristóbal; Rain-Franco, Angel; Belmar, Lucy; Fernandez, Camila

    2016-08-03

    We report the seasonal and single-diurnal variability of potentially active members of the prokaryote community in coastal surface waters off central Chile and the relationship between nitrifiers and solar radiation by combining 16S cDNA-based pyrosequencing, RT-qPCR of specific gene markers for nitrifiers (amoA, for general AOA, AOA-A, AOA-B, Nitrosopumilus maritimus and beta-AOB; and 16S rRNA gene for Nitrospina-like NOB), and solar irradiance measurements. We also evaluated the effects of artificial UVA-PAR and PAR spectra on nitrifiers by RT-qPCR. All nitrifiers (except AOA-B ecotype) were detected via RT-qPCR but AOA was the only group detected by pyrosequencing. Results showed high variability in their transcriptional levels during the day which could be associated to sunlight intensity thresholds in winter although AOA and Nitrospina-like NOB transcript number were also potentially related with environmental substrate availability. Only N. maritimus amoA transcripts showed a significant negative correlation with solar irradiances in both periods. During spring-summer, Nitrospina transcripts decreased at higher sunlight intensities, whereas the opposite was found during winter under natural (in situ) and artificial light experiments. In summary, a nitrifying community with variable tolerance to solar radiation is responsible for daily nitrification, and was particularly diverse during winter in the study area.

  14. Growth performances and changes of macronutrient ion concentrations in the culture medium when Euglena gracilis was cultured with nitrified digestate.

    PubMed

    Takemura, Kenji; Endo, Ryosuke; Shibuya, Toshio; Kitaya, Yoshiaki

    2017-09-01

    We investigated the possibility of using Euglena gracilis to convert digestate from methane fermentation of organic wastes into a medium for soilless crop culture. The growth of E. gracilis cultured with aqueous solutions containing filtrate of raw digestate at 1-30% (v/v) and nitrified digestate at 10-100% (v/v) was examined. Concentrations of plant macronutrient ions in nitrified digestate before and after culturing E. gracilis were also examined. Specific growth rates in aqueous solutions containing filtrate of raw digestate at 1-10% and nitrified digestate at 10-100% showed no significant differences, respectively (0.781 ± 0.031 d(-1) and 0.925 ± 0.033 d(-1), mean ± standard error). The rates in the filtrate of nitrified digestate were significantly higher than those in the filtrate of raw digestate. Moreover, there were no significant differences between the concentrations of plant macronutrient ions other than [Formula: see text] in the filtrate of nitrified digestate before and after culturing E. gracilis. The concentration of [Formula: see text] decreased significantly by 10.5% of the initial concentration. As a result, the constituent ratio of plant macronutrient ions other than magnesium in the solution after culturing E. gracilis was similar to that in a standard nutrient solution for soilless culture.

  15. Pyruvic Oxime Nitrification and Copper and Nickel Resistance by a Cupriavidus pauculus, an Active Heterotrophic Nitrifier-Denitrifier

    PubMed Central

    Linchangco, Richard

    2014-01-01

    Heterotrophic nitrifiers synthesize nitrogenous gasses when nitrifying ammonium ion. A Cupriavidus pauculus, previously thought an Alcaligenes sp. and noted as an active heterotrophic nitrifier-denitrifier, was examined for its ability to produce nitrogen gas (N2) and nitrous oxide (N2O) while heterotrophically nitrifying the organic substrate pyruvic oxime [CH3–C(NOH)–COOH]. Neither N2 nor N2O were produced. Nucleotide and phylogenetic analyses indicated that the organism is a member of a genus (Cupriavidus) known for its resistance to metals and its metabolism of xenobiotics. The microbe (a Cupriavidus pauculus designated as C. pauculus strain UM1) was examined for its ability to perform heterotrophic nitrification in the presence of Cu2+ and Ni2+ and to metabolize the xenobiotic phenol. The bacterium heterotrophically nitrified well when either 1 mM Cu2+ or 0.5 mM Ni2+ was present in either enriched or minimal medium. The organism also used phenol as a sole carbon source in either the presence or absence of 1 mM Cu2+ or 0.5 mM Ni2+. The ability of this isolate to perform a number of different metabolisms, its noteworthy resistance to copper and nickel, and its potential use as a bioremediation agent are discussed. PMID:25580463

  16. Activated sludge filterability improvement by nitrifying bacteria abundance regulation in an adsorption membrane bioreactor (Ad-MBR).

    PubMed

    Sun, Fei-yun; Lv, Xiao-mei; Li, Ji; Peng, Zhong-yi; Li, Pu; Shao, Ming-fei

    2014-10-01

    Autotrophic nitrifying bacteria have its intrinsic properties including low EPS production, dense colonial structure and slow-growth rate, favoring the sludge filterability improvement. An adsorption-MBR (Ad-MBR) was developed to enrich nitrifier abundance in the MBR chamber by inlet C/N regulation, and its possible positive effect on sludge filterability and underlying mechanisms were investigated. By DNA extraction, PCR amplification and Illumina high-throughput pyrosequencing, the abundance of nitrifying bacteria was accurately quantified. More than 8.29% nitrifier abundance was achieved in Ad-MBR sludge, which was above three times of that in conventional MBR. Regulated C/N ratio and thereafter nitrifier abundance enrichment improved sludge filterability by altering sludge mixture and its supernatant properties, reflected by a good sludge settleability, a low supernatant viscosity and turbidity, a low supernatant organic substances concentration, and a small amount of strong hydrophobic fractional components, thus to profoundly improve sludge filterability and decelerate membrane fouling. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Role of Multicellular Aggregates in Biofilm Formation

    PubMed Central

    Kragh, Kasper N.; Hutchison, Jaime B.; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled E. L.; Irie, Yasuhiko; Jensen, Peter Ø.; Diggle, Stephen P.; Allen, Rosalind J.

    2016-01-01

    ABSTRACT In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation. PMID:27006463

  18. Characterization of the microbial community in a lotic environment to assess the effect of pollution on nitrifying and potentially pathogenic bacteria.

    PubMed

    Medeiros, J D; Araújo, L X; da Silva, V L; Diniz, C G; Cesar, D E; Del'Duca, A; Coelho, C M

    2014-08-01

    This study aimed to investigate microbes involved in the nitrogen cycle and potentially pathogenic bacteria from urban and rural sites of the São Pedro stream. Water samples were collected from two sites. A seasonal survey of bacterial abundance was conducted. The dissolved nutrient content was analysed. PCR and FISH analysis were performed to identify and quantify microbes involved in the nitrogen cycle and potentially pathogenic bacteria. The seasonal survey revealed that the bacterial abundance was similar along the year on the rural area but varied on the urban site. Higher concentration of dissolved nutrients in the urban area indicated a eutrophic system. Considering the nitrifying microbes, the genus Nitrobacter was found, especially in the urban area, and may act as the principal bacteria in converting nitrite into nitrate at this site. The molecular markers napA, amoA, and nfrA were more accumulated at the urban site, justifying the higher content of nutrients metabolised by these enzymes. Finally, high intensity of amplicons from Enterococcus, Streptococcus, Bacteroides/Prevotella/Porphyromonas, Salmonella, S. aureus, P. aeruginosa and the diarrheagenic lineages of E. coli were observed at the urban site. These results indicate a change in the structure of the microbial community imposed by anthrophic actions. The incidence of pathogenic bacteria in aquatic environments is of particular importance to public health, emphasising the need for sewage treatment to minimise the environmental impacts associated with urbanisation.

  19. Seasonal variations in abundance of nitrifying bacteria in fish pond ecosystem.

    PubMed

    Kumari, Vibha; Rathore, Gaurav; Chauhan, U K; Pandey, A K; Lakra, W S

    2011-03-01

    Seasonal changes in abundance of nitrifiers (ammonia-oxidizing and nitrite-oxidizing bacteria) in surface and bottom water of freshwater ponds were examined with respect to temperature, DO, pH as well as concentration of ammonia and nitrite. The most probable number (MPN) of ammonia-oxidizers in different ponds varied from 1297 +/- 3.6 to 1673.23 +/- 0.36 ml(-1) in bottom and 720.5 +/- 8.1 to 955.3 +/- 10.8 ml(-1) in surface water during the rainy season while the MPN ranged from 1074 +/- 1.07 to 1372.17 +/- 4.6 ml(-1) in bottom and 515 +/- 10.1 to 678 +/- 11.8 ml(-1) in surface water in winter. However, the MPN were greatly reduced in summer and ranged from 435.05 +/- 15.7 to 547.54 +/- 2.12 ml(-1) in bottom and 218.7 +/- 7.3 to 368.4 +/- 9.32 ml(-1) in surface water. Similar seasonal trends were also observed in MPN of nitrite-oxidizers. Among all the physico-chemical parameters, abundance of nitrifiers was more positively correlated with ammonia and nitrite concentration in all the seasons. The abundance of nitrifiers in surface and bottom water was highest in rainy season followed by winter and modest in summer. The potential nitrification activities and oxidation rates were shown to be linear and activity of ammonia-oxidizing and nitrite-oxidizing bacteria was highest during rainy season.

  20. Occurrence of nitrifiers and diversity of ammonia-oxidizing bacteria in developing drinking water biofilms.

    PubMed

    Lipponen, Mari T T; Martikainen, Pertti J; Vasara, Ritva E; Servomaa, Kristina; Zacheus, Outi; Kontro, Merja H

    2004-12-01

    We studied the population dynamics of nitrifying bacteria during the development of biofilms up to 233 or 280 days on polyvinylchloride pipes connected to two full-scale drinking water distribution networks supplying processed and chloraminated surface water. The numbers of nitrifiers in biofilms were enumerated at intervals of 10-64 days by the most probable number (MPN) method at waterworks and at several study sites in distribution network areas. The numbers of nitrifiers increased towards the distal sites. The highest detected MPN counts of ammonia-oxidizing bacteria (AOB) for study areas 1 and 7 were 500 MPN cm(-2) and 1.0 x 10(6) MPN cm(-2), and those of nitrite-oxidizing bacteria (NOB) 96 MPN cm(-2) and 2.2 x 10(3) MPN cm(-2), respectively. The diversity of AOB was determined by PCR amplifying, cloning and sequencing the partial ammonia monooxygenase (amoA) gene of selected biofilm samples presenting different biofilm ages. The PCR primers used, A189 and A682, also amplified a fragment of particulate methane monooxygenase (pmoA) gene of methane-oxidizing bacteria. The majority of biofilm clones (24 out of 30 studied) contained Nitrosomonas amoA-like sequences. There were only two pmoA-like sequences of Type I methanotrophs, and four sequences positioned in amoA/pmoA sequence groups of uncultured bacteria. From both study area very similar or even completely identical Nitrosomonas amoA-like sequences were obtained despite of high difference in AOB numbers. The results show that the conditions in newly formed biofilms in drinking water distribution systems favor the growth of Nitrosomonas-type AOB.

  1. Multiscale simulation of red blood cell aggregation

    NASA Astrophysics Data System (ADS)

    Bagchi, P.; Popel, A. S.

    2004-11-01

    In humans and other mammals, aggregation of red blood cells (RBC) is a major determinant to blood viscosity in microcirculation under physiological and pathological conditions. Elevated levels of aggregation are often related to cardiovascular diseases, bacterial infection, diabetes, and obesity. Aggregation is a multiscale phenomenon that is governed by the molecular bond formation between adjacent cells, morphological and rheological properties of the cells, and the motion of the extra-cellular fluid in which the cells circulate. We have developed a simulation technique using front tracking methods for multiple fluids that includes the multiscale characteristics of aggregation. We will report the first-ever direct computer simulation of aggregation of deformable cells in shear flows. We will present results on the effect of shear rate, strength of the cross-bridging bonds, and the cell rheological properties on the rolling motion, deformation and subsequent breakage of an aggregate.

  2. Estimating nitrifying biomass in drinking water filters for surface water treatment.

    PubMed

    Tränckner, Jens; Wricke, Burkhard; Krebs, Peter

    2008-05-01

    The objective of this work is to estimate active nitrifying biomass and its main influencing factors in low-loaded biofilters based on operational data. An analytical approach based on balancing growth, decay and biomass removed by backwashing is proposed. The method is developed and applied in pilot-scale rapid sand filters for drinking water treatment. Decay rate was measured directly in the filter for different temperatures. To assess the amount of active biomass in backwash water, a technique based on respiration measurements was used. Backwash losses increased overproportional with balanced biomass in the filter. The impact of both parameters on active biomass is quantified exemplarily for a given constant nitrification rate.

  3. Application of toxicity monitor using nitrifying bacteria biosensor to sewerage systems.

    PubMed

    Inui, T; Tanaka, Y; Okayas, Y; Tanaka, H

    2002-01-01

    Toxic substances may be included in wastewater influent and can damage biological processing of wastewater treatment, therefore continuous toxic-monitoring of wastewater influent is needed. This paper describes the potential toxic-monitoring applications of the toxicity monitor using a nitrifying bacteria biosensor to sewerage systems. The results of sensitivity tests show that aspects of wastewater do not affect the sensor sensitivity and confirm that the sensor can be applied to wastewater monitoring as it is. The monitor with a prototype of filtration system installed in a wastewater treatment plant is able to operate continuously for one month at least after the modification of filtration system and the optimization of operation conditions.

  4. Development of Novel Random Network Theory-Based Approaches to Identify Network Interactions among Nitrifying Bacteria

    SciTech Connect

    Shi, Cindy

    2015-07-17

    The interactions among different microbial populations in a community could play more important roles in determining ecosystem functioning than species numbers and their abundances, but very little is known about such network interactions at a community level. The goal of this project is to develop novel framework approaches and associated software tools to characterize the network interactions in microbial communities based on high throughput, large scale high-throughput metagenomics data and apply these approaches to understand the impacts of environmental changes (e.g., climate change, contamination) on network interactions among different nitrifying populations and associated microbial communities.

  5. Meso and micro-scale response of post carbon removal nitrifying MBBR biofilm across carrier type and loading.

    PubMed

    Young, Bradley; Banihashemi, Bahman; Forrest, Daina; Kennedy, Kevin; Stintzi, Alain; Delatolla, Robert

    2016-03-15

    This study investigates the effects of three specific moving bed biofilm reactor (MBBR) carrier types and two surface area loading rates on biofilm thickness, morphology and bacterial community structure of post carbon removal nitrifying MBBR systems along with the effects of carrier type and loading on ammonia removal rates and effluent solids settleability. The meso and micro analyses show that the AOB kinetics vary based on loading condition, but irrespective of carrier type. The meso-scale response to increases in loading was shown to be an increase in biofilm thickness with higher surface area carriers being more inclined to develop and maintain thicker biofilms. The pore spaces of these higher surface area to volume carriers also demonstrated the potential to become clogged at higher loading conditions. Although the biofilm thickness increased during higher loading conditions, the relative percentages of both the embedded viable and non-viable cells at high and conventional loading conditions remained stable; indicating that the reduced ammonia removal kinetics observed during carrier clogging events is likely due to the observed reduction in the surface area of the attached biofilm. Microbial community analyses demonstrated that the dominant ammonia oxidizing bacteria for all carriers is Nitrosomonas while the dominant nitrite oxidizing bacteria is Nitrospira. The research showed that filamentous species were abundant under high loading conditions, which likely resulted in the observed reduction in effluent solids settleability at high loading conditions as opposed to conventional loading conditions. Although the settleability of the effluent solids was correlated to increases in abundances of filamentous organisms in the biofilm, analyzed using next generation sequencing, the ammonia removal rate was not shown to be directly correlated to specific meso or micro-scale characteristics. Instead post carbon removal MBBR ammonia removal kinetics were shown to be

  6. Monochloramine Cometabolism by Mixed-Culture Nitrifiers under Drinking Water Conditions.

    PubMed

    Maestre, Juan P; Wahman, David G; Speitel, Gerald E

    2016-06-21

    Chloramines are the second most used secondary disinfectant by United States water utilities. However, chloramination may promote nitrifying bacteria. Recently, monochloramine cometabolism by the pure culture ammonia-oxidizing bacteria, Nitrosomonas europaea, was shown to increase monochloramine demand. The current research investigated monochloramine cometabolism by nitrifying mixed cultures grown under more relevant drinking water conditions and harvested from sand-packed reactors before conducting suspended growth batch kinetic experiments. Four types of batch kinetic experiments were conducted: (1) positive controls to estimate ammonia kinetic parameters, (2) negative controls to account for biomass reactivity, (3) utilization associated product (UAP) controls to account for UAP reactivity, and (4) cometabolism experiments to estimate cometabolism kinetic parameters. Kinetic parameters were estimated in AQUASIM with a simultaneous fit to the experimental data. Cometabolism kinetics were best described by a first-order model. Monochloramine cometabolism kinetics were similar to those of ammonia metabolism, and monochloramine cometabolism accounted for 30% of the observed monochloramine loss. These results demonstrated that monochloramine cometabolism occurred in mixed cultures similar to those found in drinking water distribution systems; therefore, monochloramine cometabolism may be a significant contribution to monochloramine loss during nitrification episodes in drinking water distribution systems.

  7. Analysis of microbial community and nitrogen transition with enriched nitrifying soil microbes for organic hydroponics.

    PubMed

    Saijai, Sakuntala; Ando, Akinori; Inukai, Ryuya; Shinohara, Makoto; Ogawa, Jun

    2016-06-27

    Nitrifying microbial consortia were enriched from bark compost in a water system by regulating the amounts of organic nitrogen compounds and by controlling the aeration conditions with addition of CaCO3 for maintaining suitable pH. Repeated enrichment showed reproducible mineralization of organic nitrogen via the conversion of ammonium ions ([Formula: see text]) and nitrite ions ([Formula: see text]) into nitrate ions ([Formula: see text]). The change in microbial composition during the enrichment was investigated by PCR-DGGE analysis with a focus on prokaryote, ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and eukaryote cell types. The microbial transition had a simple profile and showed clear relation to nitrogen ions transition. Nitrosomonas and Nitrobacter were mainly detected during [Formula: see text] and [Formula: see text] oxidation, respectively. These results revealing representative microorganisms acting in each ammonification and nitrification stages will be valuable for the development of artificial simple microbial consortia for organic hydroponics that consisted of identified heterotrophs and autotrophic nitrifying bacteria.

  8. Comparative study of the nitrification characteristics of two different nitrifier immobilization methods.

    PubMed

    Li, Zhirong; Zhang, Zhi; Li, Jun; Zhang, Zhenjia

    2009-11-01

    The research investigated the nitrification characteristics of two different immobilization methods: nitrifier encapsulation in polyethylene glycol (PEG) gel pellets and nitrifier biofilm attachment on elastic plastic filler. The two carriers were placed in identical reactors. They reached a maximum nitrification rate of 39 and 25 mgN/L.h 30 days after start-up. The results showed that the nitrification efficiency in the PEG reactor was higher than in the biofilm reactor under the same conditions. Variations in temperature decreased the nitrification rate by approximately 55% in the PEG reactor from 28 to 8 degrees C, while 74.2% in the biofilm reactor. When the COD loading rate was increased to 0.8 kg/m(3) day, the nitrification efficiency in the biofilm reactor dropped sharply to 23%, and that of PEG reactor remained over 80%. PEG pellets with a high nitrification rate under all conditions showed promise as an immobilization medium, and are likely to be utilized in the nitrification of high-strength ammonia and COD wastewater during long-term operation.

  9. Nitrogen Redox Metabolism of a Heterotrophic, Nitrifying-Denitrifying Alcaligenes sp. from Soil

    PubMed Central

    Castignetti, Domenic; Hollocher, Thomas C.

    1982-01-01

    Metabolic characteristics of a heterotrophic, nitrifier-denitrifier Alcaligenes sp. isolated from soil were further characterized. Pyruvic oxime and hydroxylamine were oxidized to nitrite aerobically by nitrification-adapted cells with specific activities (Vmax) of 0.066 and 0.003 μmol of N × min−1 × mg of protein−1, respectively, at 22°C. Km values were 15 and 42 μM for pyruvic oxime and hydroxylamine, respectively. The greater pyruvic oxime oxidation activity relative to hydroxylamine oxidation activity indicates that pyruvic oxime was a specific substrate and was not oxidized appreciably via its hydrolysis product, hydroxylamine. When grown as a denitrifier on nitrate, the bacterium could not aerobically oxidize pyruvic oxime or hydroxylamine to nitrite. However, hydroxylamine was converted to nearly equimolar amounts of ammonium ion and nitrous oxide, and the nature of this reaction is discussed. Cells grown as heterotrophic nitrifiers on pyruvic oxime contained two enzymes of denitrification, nitrate reductase and nitric oxide reductase. The nitrate reductase was the dissimilatory type, as evidenced by its extreme sensitivity to inhibition by azide and by its ability to be reversibly inhibited by oxygen. Cells grown aerobically on organic carbon sources other than pyruvic oxime contained none of the denitrifying enzymes surveyed but were able to oxidize pyruvic oxime to nitrite and reduce hydroxylamine to ammonium ion. PMID:16346117

  10. Evidence of soluble microbial products accelerating chloramine decay in nitrifying bulk water samples.

    PubMed

    Bal Krishna, K C; Sathasivan, Arumugam; Chandra Sarker, Dipok

    2012-09-01

    The discovery of a microbially derived soluble product that accelerates chloramine decay is described. Nitrifying bacteria are believed to be wholly responsible for rapid chloramine loss in drinking water systems. However, a recent investigation showed that an unidentified soluble agent significantly accelerated chloramine decay. The agent was suspected to be either natural organic matter (NOM) or soluble microbial products (SMPs). A laboratory scale reactor was fed chloraminated reverse osmosis (RO) treated water to eliminate the interference from NOM. Once nitrification had set in, experiments were conducted on the reactor and feed waters to determine the identity of the component. The study showed the presence of SMPs released by microbes in severely nitrified waters. Further experiments proved that the SMPs significantly accelerated chloramine decay, probably through catalytic reaction. Moreover, application of common protein denaturing techniques stopped the reaction implying that the compound responsible was likely to be a protein. This significant finding will pave the way for better control of chloramine in the distribution systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Congruence in the performance of model nitrifying activated sludge plants located in Germany, Scotland and Spain.

    PubMed

    Christofi, Nick; Aspichueta, Elena; Dalzell, David; De la Sota, Alejandro; Etxebarria, Javier; Fernandes, Teresa; Gutierrez, Monica; Morton, John; Obst, Ursula; Schmellenkamp, Peter

    2003-01-01

    A laboratory model nitrifying activated sludge plant treating OECD synthetic sewage was designed and constructed by each of three laboratories in Germany, Scotland and Spain in order to produce a sludge inoculum for 5 rapid toxicity bioassays. The plants were run for 3 years and produced sludge for the microbially based bioassays Vibrio fischeri bioluminescence, ATP luminescence and respiration, and, nitrification and enzyme inhibition. Although the initial sludge inoculum for the plants differed, as did some of the running conditions such as temperature regime, the sludge produced within the different countries had similar characteristics with respect to sludge age, total suspended solids and volatile suspended solids. Nitrification was generally maintained over the 3-year period although there were occasions when the process was inconsistent. Nitrification recovery was afforded by reseeding with a nitrifying sludge from a local wastewater treatment works (WWTW) or imposition of starvation conditions for a period of time. The sludge produced was used to carry out toxicity testing and results compared well with those using sludge from a WWTW. Overall, the use of sludge generated in the laboratory could be used for toxicity testing negating the need to resort to the use of natural WWTW sludge, which may contain a range of toxic substances due to uncontrolled industrial and domestic inputs and an unbalanced microbial consortium.

  12. Production of NO2/-/ and N2O by nitrifying bacteria at reduced concentrations of oxygen

    NASA Technical Reports Server (NTRS)

    Goreau, T. J.; Kaplan, W. A.; Wofsy, S. C.; Mcelroy, M. B.; Valois, F. W.; Watson, S. W.

    1980-01-01

    The influence of oxygen concentration on the production of NO2(-) and N2O by nitrifying marine bacteria of the genus Nitrosomonas is investigated. Pure cultures of the ammonium-oxiding bacteria isolated from the Western Tropical Atlantic Ocean were grown at oxygen partial pressures from 0.005 to 0.2 atm, and concentrations of N2O in the air above the growth medium and dissolved NO2(-) were determined. Decreasing oxygen concentrations are observed to induce a marked decrease in NO2(-) production rates and increase in N2O evolution, leading to an increase of the relative yield of N2O with respect to NO2(-) from 0.3% to nearly 10%. Similar yields of N2O at atmospheric oxygen levels are found for nitrifying bacteria of the genera Nitrosomonas, Nitrosolobus, Nitrosospira and Nitrosococcus, while nitrite-oxydizing bacteria and a dinoflagellate did not produce detectable quantities of N2O. Results support the view that nitrification is a major source of N2O in the environment.

  13. Effectiveness of breakpoint chlorination to reduce accelerated chemical chloramine decay in severely nitrified bulk waters.

    PubMed

    Bal Krishna, K C; Sathasivan, Arumugam; Kastl, George

    2014-12-01

    Rectifying the accelerated chloramine decay after the onset of nitrification is a major challenge for water utilities that employ chloramine as a disinfectant. Recently, the evidence of soluble microbial products (SMPs) accelerating chloramine decay beyond traditionally known means was reported. After the onset of nitrification, with an intention to inactivate nitrifying bacteria and thus maintaining disinfectant residuals, breakpoint chlorination followed by re-chloramination is usually practiced by water utilities. However, what actually breakpoint chlorination does beyond known effects is not known, especially in light of the new finding of SMPs. In this study, experiments were conducted using severely nitrified chloraminated water samples (chloramine residuals <0.5 mg Cl2 L−1, nitrite residuals >0.1 mg N L−1 and an order of magnitude higher chloramine decay rate compared to normal decay) obtained from two laboratory scale systems operated by feeding natural organic matter (NOM) containing and NOM free waters. Results showed that the accelerated decay of chloramine as a result of SMPs can be eliminated by spiking higher free chlorine residuals (about 0.92 ± 0.03 to 1.16 ± 0.12 mg Cl2 L−1) than the stoichiometric requirement for breakpoint chlorination and nitrite oxidation. Further, accelerated initial chlorine decay showed chlorine preferentially reacts with nitrite and ammonia before destroying SMPs. This study, clearly demonstrated there is an additional demand from SMPs that needs to be satisfied to effectively recover disinfection residuals in subsequent re-chloramination.

  14. Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Dual Energy-Limited Chemostats

    PubMed Central

    Verhagen, Frank J. M.; Laanbroek, Hendrikus J.

    1991-01-01

    The absence of nitrification in soils rich in organic matter has often been reported. Therefore, competition for limiting amounts of ammonium between the chemolithotrophic ammonium-oxidizing species Nitrosomonas europaea and the heterotrophic species Arthrobacter globiformis was studied in the presence of Nitrobacter winogradskyi in continuous cultures at dilution rates of 0.004 and 0.01 h−1. Ammonium limitation of A. globiformis was achieved by increasing the glucose concentration in the reservoir stepwise from 0 to 5 mM while maintaining the ammonium concentration at 2 mM. The numbers of N. europaea and N. winogradskyi cells decreased as the numbers of heterotrophic bacteria rose with increasing glucose concentrations for both dilution rates. Critical carbon-to-nitrogen ratios of 11.6 and 9.6 were determined for the dilution rates of 0.004 and 0.01 h−1, respectively. Below these critical values, coexistence of the competing species was found in steady-state situations. Although the numbers were strongly reduced, the nitrifying bacteria were not fully outcompeted by the heterotrophic bacteria above the critical carbon-to-nitrogen ratios. Nitrifying bacteria could probably maintain themselves in the system above the critical carbon-to-nitrogen ratios because they are attached to the glass wall of the culture vessels. The numbers of N. europaea decreased more than did those of N. winogradskyi. This was assumed to be due to heterotrophic growth of the latter species on organic substrates excreted by the heterotrophic bacteria. PMID:16348588

  15. Properties of some reductase enzymes in the nitrifying bacteria and their relationship to the oxidase systems

    PubMed Central

    Wallace, W.; Nicholas, D. J. D.

    1968-01-01

    The reductase enzymes in Nitrosomonas and Nitrobacter were studied under anaerobic conditions when the oxidase enzymes were inactive. The most effective electron-donor systems for nitrate reductase in Nitrobacter were reduced benzyl viologen alone, phenazine methosulphate with either NADH or NADPH, and FMN or FAD with NADH. Nitrite and hydroxylamine reductases were found in both nitrifying bacteria, and optimum activity for each enzyme was obtained with NADH or NADPH with either FMN or FAD. The product of both these enzymes was identified as ammonia. In extracts of Nitrosomonas the ammonia was further utilized by an NADPH-specific glutamate dehydrogenase. 15N-labelled nitrite, hydroxylamine and ammonia were rapidly incorporated into cell protein by Nitrosomonas, and Nitrobacter in addition incorporated [15N]nitrate. Relatively gentle methods of cell disruption were compared with ultrasonic treatment, to enable a more exact study to be undertaken of the intracellular distribution of the oxidase and reductase enzymes. The functional relationship of these opposing enzyme systems in the nitrifying bacteria is considered. PMID:4386932

  16. Impact of prehybridization PCR amplification on microarray detection of nitrifying bacteria in wastewater treatment plant samples.

    PubMed

    Siripong, Slil; Kelly, John J; Stahl, David A; Rittmann, Bruce E

    2006-09-01

    A gel-based microarray that included a set of 26 oligonucleotide probes targeting all nitrifying bacteria at varying levels of specificity suggested the presence of targeted microorganisms when hybridized to RNA isolated from a wastewater treatment plant, but could not discriminate between perfectly matched and mismatched sequences due in part to low signal intensity. To enhance sensitivity and improve discrimination, polymerase chain reaction was used to selectively amplify the 16S rRNA genes of specific nitrifier groups. RNA transcribed from these DNA templates was hybridized to the microarray and thermal dissociation analysis was used to characterize the specificity of hybridization. Amplification with Nitrospira-specific primers resulted in the selective amplification of this target group, confirmed by both a significant increase in signal intensity and a melting profile identical to the reference RNA. In contrast, Nitrobacter was not detected in the environmental samples with probe Nbac1000 despite pre-amplification with Nitrobacter-specific primers, indicating the absence of strains containing this Nitrobacter-specific sequence. Pre-amplification using primers specific for beta-Proteobacterial ammonia-oxidizing bacteria resulted in a significant increase in signal intensity for probe Nso190, but melting profiles for probe Nso190 showed a slight deviation between amplified RNA and the reference microorganism, suggesting that the amplification products contained some sequences that varied by a single nucleotide difference in the probe target region.

  17. Production of NO2/-/ and N2O by nitrifying bacteria at reduced concentrations of oxygen

    NASA Technical Reports Server (NTRS)

    Goreau, T. J.; Kaplan, W. A.; Wofsy, S. C.; Mcelroy, M. B.; Valois, F. W.; Watson, S. W.

    1980-01-01

    The influence of oxygen concentration on the production of NO2(-) and N2O by nitrifying marine bacteria of the genus Nitrosomonas is investigated. Pure cultures of the ammonium-oxiding bacteria isolated from the Western Tropical Atlantic Ocean were grown at oxygen partial pressures from 0.005 to 0.2 atm, and concentrations of N2O in the air above the growth medium and dissolved NO2(-) were determined. Decreasing oxygen concentrations are observed to induce a marked decrease in NO2(-) production rates and increase in N2O evolution, leading to an increase of the relative yield of N2O with respect to NO2(-) from 0.3% to nearly 10%. Similar yields of N2O at atmospheric oxygen levels are found for nitrifying bacteria of the genera Nitrosomonas, Nitrosolobus, Nitrosospira and Nitrosococcus, while nitrite-oxydizing bacteria and a dinoflagellate did not produce detectable quantities of N2O. Results support the view that nitrification is a major source of N2O in the environment.

  18. Collapsing bacterial cylinders

    NASA Astrophysics Data System (ADS)

    Betterton, M. D.; Brenner, Michael P.

    2001-12-01

    Under special conditions bacteria excrete an attractant and aggregate. The high density regions initially collapse into cylindrical structures, which subsequently destabilize and break up into spherical aggregates. This paper presents a theoretical description of the process, from the structure of the collapsing cylinder to the spacing of the final aggregates. We show that cylindrical collapse involves a delicate balance in which bacterial attraction and diffusion nearly cancel, leading to corrections to the collapse laws expected from dimensional analysis. The instability of a collapsing cylinder is composed of two distinct stages: Initially, slow modulations to the cylinder develop, which correspond to a variation of the collapse time along the cylinder axis. Ultimately, one point on the cylinder pinches off. At this final stage of the instability, a front propagates from the pinch into the remainder of the cylinder. The spacing of the resulting spherical aggregates is determined by the front propagation.

  19. Structure of nitrifying biofilms in a high-rate trickling filter designed for potable water pre-treatment.

    PubMed

    van den Akker, Ben; Holmes, Mike; Pearce, Peter; Cromar, Nancy J; Fallowfield, Howard J

    2011-05-01

    This study examined the composition and structure of nitrifying biofilms sampled from a high-rate nitrifying trickling filter which was designed to pre-treat raw surface water for potable supply. The filter was operated under a range of feed water ammonia and organic carbon concentrations that mimicked the raw water quality of poorly protected catchments. The biofilm structure was examined using a combination of fluorescence in situ hybridisation and scanning electron microscopy. Biopolymers (carbohydrate and protein) were also measured. When the filter was operated under low organic loads, nitrifiers were abundant, representing the majority of microorganisms present. Uniquely, the study identified not only Nitrospira but also the less common Nitrobacter. Small increases in organic carbon promoted the rapid growth of filamentous heterotrophs, as well as the production of large amounts of polysaccharide. Stratification of nitrifiers and heterotrophs, and high polysaccharide were observed at all filter bed depths, which coincided with the impediment of nitrification throughout most of the filter bed. Observations presented here specifically linked biofilm structure with filter functionality, physically validating previous empirical modelling hypotheses regarding competitive interactions between autotrophic and heterotrophic bacteria in biofilms. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Microbial aggregates in anaerobic wastewater treatment.

    PubMed

    Kosaric, N; Blaszczyk, R

    1990-01-01

    The phenomenon aggregation of anaerobic bacteria gives an opportunity to speed up the digestion rate during methanogenesis. The aggregates are mainly composed of methanogenic bacteria which convert acetate and H2/CO2 into methane. Other bacteria are also included in the aggregates but their concentration is rather small. The aggregates may also be formed during acetogenesis or even hydrolysis but such aggregates are not stable and disrupt quickly when not fed. A two stage process seems to be suitable when high concentrated solid waste must be treated. Special conditions are necessary to promote aggregate formation from methanogenic bacteria but aggregates once formed are stable without feeding even for a few years. The structure, texture and activity of bacterial aggregates depend on several parameters: (1)--temperature and pH, (2)--wastewater composition and (3)--hydrodynamic conditions within the reactor. The common influence of all these parameters is still rather unknown but some recommendations may be given. Temperature and pH should be maintained in the range which is optimal for methanogenic bacteria e.g. a temperature between 32 and 50 degrees C and a value pH between 6.5 and 7.5. Wastewaters should contain soluble wastes and the specific loading rate should be around one kgCOD(kgVSS)-1 d-1. The concentration of the elements influences aggregate composition and probably structure and texture. At high calcium concentration a change in the colour of the granules has been observed. Research is necessary to investigate the influence of other elements and organic toxicants on maintenance of the aggregates. Hydrodynamic conditions seem to influence the stability of the granules over long time periods. At low liquid stream rates, aggregates may starve and lysis within the aggregates is possible which results in hollowing of aggregates and their floating. At high liquid stream rates the aggregates may be disrupted and washed out of the reactor as a flocculent

  1. Synthesis of 2-furyl-4-arylidene-5(4H)-oxazolones as new potent antibacterial agents against phyto-pathogenic and nitrifying bacteria.

    PubMed

    Thombare, Nandkishore S; Aggarwal, Nisha; Kumar, Rajesh; Gopal, Madhuban

    2012-01-01

    Crop losses due to bacterial pathogens are a major global concern. Most of the available pesticides for these pathogens suffer from various drawbacks such as complicated synthesis, high cost, high toxicity, pesticide resistance and environmental hazards. To overcome these drawbacks, the present study was undertaken to find a potent bactericide. Therefore, a series of compounds comprising bioactive furyl and oxazolone rings was synthesized under microwave irradiation and screened for in vitro antibacterial activity. The reactions were completed in fewer than 2 minutes with minimal use of solvents and resulted in high yields. These compounds were screened for antibacterial activity against plant pathogens, Xanthomonas oryzae, Ralstonia solanacearum and nitrifying bacteria, Nitrosomonas species under laboratory conditions. Five compounds were active as antibacterial agents against Xanthomonas oryzae and Ralstonia solanacearum. However, all compounds were effective against the Nitrosomonas species and the best one was 2-furyl-4-(3-methoxy-4-hydroxybenzylidene)-5(4H)-oxazolone. The study revealed the fast and environmentally friendly synthesis of bioactive title compounds, which also hold promise to be used as prototypes for the discovery of potent analogues.

  2. The use of microsensors to study the role of the loading rate and surface velocity on the growth and the composition of nitrifying biofilms.

    PubMed

    Gonzalez, B C; Spinola, A L G; Lamon, A W; Araujo, J C; Campos, J R

    2011-01-01

    The good composition and activity of biofilms are very important for successful operation and control of fixed-film biological reactors employed in liquid effluents treatment. During the last decade, microsensors have been applied to study microbial ecology. These sensors could provide information regarding the microbial activity concerning nitrification and denitrification that occur inside biofilms. Other techniques of molecular biology, such as fluorescence in situ hybridization (FISH), have also contributed to this matter because their application aids in the identification of the bacterial populations that compose the biofilms. The focus of this paper was to study the loading rate and surface velocity to promote the development of nitrifying biofilms in three distinct flow cells that were employed in the post treatment of a synthetic wastewater simulating the effluent from a UASB (Upflow Anaerobic Sludge Blanket) reactor. Using the FISH technique, it was found that the population of ammonia-oxidizing-bacteria was greater than that of nitrite-oxidizing-bacteria; this was also supported by the lower production of nitrate determined by physicochemical and microsensor analyses. It was verified that the loading rate and surface velocity that promoted the greatest nitrogen removal were 0.25 g N-amon m(-2)biofilm day(-1) and 1 m h(-1), respectively.

  3. Achieving nitrogen removal via nitrite pathway from urban landfill leachate using the synergetic inhibition of free ammonia and free nitrous acid on nitrifying bacteria activity.

    PubMed

    Sun, H W; Bai, Y; Peng, Y Z; Xie, H G; Shi, X N

    2013-01-01

    In this study, a biological system consisting of an up-flow anaerobic sludge blanket (UASB) and anoxic-oxic (A/O) reactor was established for the advanced treatment of high ammonium urban landfill leachate. The inhibitory effect of free ammonia (FA) and free nitrous acid (FNA) on the nitrifying bacterial activity was used to achieve stable nitritation in the A/O reactor. The results demonstrated that the biological system achieved chemical oxygen demand (COD), total nitrogen (TN) and NH(4)(+)-N removal efficiencies of 95.3, 84.6 and 99.2%, respectively at a low carbon-to-nitrogen ratio of 3:1. Simultaneous denitritation and methanogenesis in the UASB could improve the removal of COD and TN. Nitritation with above 90% nitrite accumulation was successfully achieved in the A/O reactor by synergetic inhibition of FA and FNA on the activity of nitrite oxidizing bacteria (NOB). Fluorescence in situ hybridization (FISH) analysis showed that ammonia oxidizing bacteria (AOB) was dominant and was considered to be responsible for the satisfactory nitritation performance.

  4. Modelling the fate of nitrite in an urbanized river using experimentally obtained nitrifier growth parameters.

    PubMed

    Raimonet, Mélanie; Vilmin, Lauriane; Flipo, Nicolas; Rocher, Vincent; Laverman, Anniet M

    2015-04-15

    Maintaining low nitrite concentrations in aquatic systems is a major issue for stakeholders due to nitrite's high toxicity for living species. This study reports on a cost-effective and realistic approach to study nitrite dynamics and improve its modelling in human-impacted river systems. The implementation of different nitrifying biomasses to model riverine communities and waste water treatment plant (WWTP)-related communities enabled us to assess the impact of a major WWTP effluent on in-river nitrification dynamics. The optimal kinetic parameters and biomasses of the different nitrifying communities were determined and validated by coupling laboratory experiments and modelling. This approach was carried out in the Seine River, as an example of a large human-impacted river with high nitrite concentrations. The simulation of nitrite fate was performed at a high spatial and temporal resolution (Δt = 10 min, dx¯ = 500 m) including water and sediment layers along a 220 km stretch of the Seine River for a 6-year period (2007-2012). The model outputs were in good agreement with the peak of nitrite downstream the WWTP as well as its slow decrease towards the estuary. Nitrite persistence between the WWTP and the estuary was mostly explained by similar production and consumption rates of nitrite in both water and sediment layers. The sediment layer constituted a significant source of nitrite, especially during high river discharges (0.1-0.4 mgN h(-1) m(-2)). This points out how essential it is to represent the benthic layer in river water quality models, since it can constitute a source of nitrite to the water-column. As a consequence of anthropogenic emissions and in-river processes, nitrite fluxes to the estuary were significant and varied from 4.1 to 5.5 TN d(-1) in low and high water discharge conditions, respectively, over the 2007-2012 period. This study provides a methodology that can be applied to any anthropized river to realistically parametrize autochthonous

  5. Archaeal and Bacterial Diversity and Enzymatic Activities Associated With Particulate Matter in the Laptev Sea, a River-Impacted Arctic Shelf Environment

    NASA Astrophysics Data System (ADS)

    Evans, C. T.; Deming, J. W.

    2006-12-01

    Arctic Ocean shelves are influenced by riverine input of terrestrial, relatively refractory particulate organic matter (POM) as well as fresh material from marine phytoplankton blooms. The fate of organic particles and aggregates depends in large part on their associated microbes and the effectiveness of hydrolytic enzymes. The Laptev Sea provides an ideal setting to test for connections between Archaeal and Bacterial communities, the quality of the POM they colonize, and the activities of extracellular enzymes. Aboard the Russian icebreaker Kapitan Dranitsyn during the NABOS 2005 cruise to the Laptev Sea, we sampled various size fractions of particulate matter, from 0.2 to 70 μm. Patterns of Archaeal and Bacterial diversity were analyzed using terminal restriction fragment length polymorphism (T-RFLP). Extracellular enzymatic activities were evaluated using fluorescent substrate analogs. Thus far, we have observed a statistically significant difference between particle-associated and free-living Bacteria, many of which appear (by clone library) to be gamma-proteobacteria or CFB. Bacterial community richness associated with the largest particle fractions, where protease and glucosidase activities were the highest, was best explained by indicators of primary productivity (chlorophyll a and phaeopigments), while richness associated with smaller size fractions was best explained by general particle indicators (and depth and salinity). In contrast, particle-associated Archaea were not significantly different from their free-living counterparts. Archaeal clone library results indicate a predominance of Marine Group 1 Crenarchaea, the group containing a recently isolated nitrifying Archaeon. Given all these results, we hypothesize that in the Laptev Sea cold-active Bacteria are the primary agents in the enzymatic degradation of POM, whether terrestrial or marine, while Archaea play other roles in the elemental cycles of Arctic waters, perhaps especially in the nitrogen

  6. Diversity in the Ammonia-Oxidizing Nitrifier Population of a Soil †

    PubMed Central

    Belser, L. W.; Schmidt, E. L.

    1978-01-01

    Multiple genera of ammonia-oxidizing chemoautotrophic nitrifiers in a soil were detected, isolated, and studied by means of modified most-probable-number (MPN) techniques. The soil examined was a Waukegon silt loam treated with ammonium nitrate or sewage effluent. The genera Nitrosomonas and Nitrosospira were found to occur more commonly than the genus Nitrosolobus. Three different MPN media gave approximately the same overall ammonia oxidizer counts within statistical error after prolonged incubation but differed markedly in ratios of Nitrosomonas to Nitrosospira. Selectivity and counting efficiency of MPN media were studied by observing the growth response of representative pure cultures isolated from the soil. Selectivity was evident in each medium with respect to all strains tested, and the media differed greatly in incubation times required to obtain maximum counts. PMID:16345319

  7. Detachment of solids and nitrifiers in integrated, fixed-film activated sludge systems.

    PubMed

    Maas, Carol L A; Parker, Wayne J; Legge, Raymond L

    2008-12-01

    Despite the importance of detachment to biofilm processes, detachment phenomena are not well understood. In this study, researchers investigated biofilm detachment from free-floating biofilm carriers that were established in an integrated, fixed-film activated sludge (IFAS) installation in Mississauga, Ontario. A method for assessing detachment from biofilm carrier systems was devised, evaluated, and refined during this study. In the absence of substrate, superficial air velocity significantly affected the 24-hour detachment rates of total suspended solids from the carriers. Short-term growth conditions did not appear to significantly affect the rate of detachment of solids and nitrifiers. The measured solids-detachment rates were found to be described by a second order function of biofilm attached growth total solids with a detachment coefficient of 0.006 +/- 0.0008 (g/m x d)(-1).

  8. Stimulatory Effect of Xenobiotics on Oxidative Electron Transport of Chemolithotrophic Nitrifying Bacteria Used as Biosensing Element

    PubMed Central

    Woznica, Andrzej; Nowak, Agnieszka; Ziemski, Przemyslaw; Kwasniewski, Mirosław; Bernas, Tytus

    2013-01-01

    Electron transport chain (ETCh) of ammonium (AOB) and nitrite oxidizing bacteria (NOB) participates in oxidation of ammonium to nitrate (nitrification). Operation of ETCh may be perturbed by a range of water-soluble xenobiotics. Therefore, consortia of nitrifying bacteria may be used as a biosensor to detect water contamination. A surprising feature of this system is an increase of oxygen consumption, detected in the presence of certain inhibitors of ETCh. Thus, to shed light on the mechanism of this effect (and other differences between inhibitors) we monitored separately respiration of the bacteria of the first (AOB - Nitrosomonas) and second (NOB -Nitrobacter) stages of nitrification. Furthermore, we measured plasma membrane potential and the level of reduction of NAD(P)H. We propose a novel model of ETCh in NOB to explain the role of reverse electron transport in the stimulation of oxygen consumption (previously attributed to hormesis). PMID:23326438

  9. Pseudomonas aeruginosa and Achromobacter sp.: nitrifying aerobic denitrifiers have a plasmid encoding for denitrifying functional genes.

    PubMed

    Kathiravan, V; Krishnani, K K

    2014-04-01

    In the present work, novel heterotrophic nitrifying and aerobic denitrifying bacteria have been isolated from greenwater system of coastal aquaculture. Based on the 16S rRNA gene, FAME analysis and biochemical test, the isolates have been identified as Pseudomonas aeruginosa and Achromobacter sp. These have been named as P. aeruginosa strain DBT1BNH3 and Achromobacter sp. strain DBTN3. Denitrifying functional genes such as nitrite reductase (nirS), nitric oxide reductase (qnorB) and nitrous oxide reductase (nosZ) genes have been identified. These strains found to have a 27 kb plasmid coding for nirS and nosZ. The possibility of horizontal transfer of plasmid among Pseudomonadaceae and Alcaligenaceae families in coastal aquaculture has been explored. Further, we have studied combined nitrification and oxygen tolerant denitrification potential in the same isolates.

  10. Stimulatory effect of xenobiotics on oxidative electron transport of chemolithotrophic nitrifying bacteria used as biosensing element.

    PubMed

    Woznica, Andrzej; Nowak, Agnieszka; Ziemski, Przemyslaw; Kwasniewski, Mirosław; Bernas, Tytus

    2013-01-01

    Electron transport chain (ETCh) of ammonium (AOB) and nitrite oxidizing bacteria (NOB) participates in oxidation of ammonium to nitrate (nitrification). Operation of ETCh may be perturbed by a range of water-soluble xenobiotics. Therefore, consortia of nitrifying bacteria may be used as a biosensor to detect water contamination. A surprising feature of this system is an increase of oxygen consumption, detected in the presence of certain inhibitors of ETCh. Thus, to shed light on the mechanism of this effect (and other differences between inhibitors) we monitored separately respiration of the bacteria of the first (AOB - Nitrosomonas) and second (NOB -Nitrobacter) stages of nitrification. Furthermore, we measured plasma membrane potential and the level of reduction of NAD(P)H. We propose a novel model of ETCh in NOB to explain the role of reverse electron transport in the stimulation of oxygen consumption (previously attributed to hormesis).

  11. Estimation of nitrite in source-separated nitrified urine with UV spectrophotometry.

    PubMed

    Mašić, Alma; Santos, Ana T L; Etter, Bastian; Udert, Kai M; Villez, Kris

    2015-11-15

    Monitoring of nitrite is essential for an immediate response and prevention of irreversible failure of decentralized biological urine nitrification reactors. Although a few sensors are available for nitrite measurement, none of them are suitable for applications in which both nitrite and nitrate are present in very high concentrations. Such is the case in collected source-separated urine, stabilized by nitrification for long-term storage. Ultraviolet (UV) spectrophotometry in combination with chemometrics is a promising option for monitoring of nitrite. In this study, an immersible in situ UV sensor is investigated for the first time so to establish a relationship between UV absorbance spectra and nitrite concentrations in nitrified urine. The study focuses on the effects of suspended particles and saturation on the absorbance spectra and the chemometric model performance. Detailed analysis indicates that suspended particles in nitrified urine have a negligible effect on nitrite estimation, concluding that sample filtration is not necessary as pretreatment. In contrast, saturation due to very high concentrations affects the model performance severely, suggesting dilution as an essential sample preparation step. However, this can also be mitigated by simple removal of the saturated, lower end of the UV absorbance spectra, and extraction of information from the secondary, weaker nitrite absorbance peak. This approach allows for estimation of nitrite with a simple chemometric model and without sample dilution. These results are promising for a practical application of the UV sensor as an in situ nitrite measurement in a urine nitrification reactor given the exceptional quality of the nitrite estimates in comparison to previous studies.

  12. A paradigm shift towards low-nitrifying production systems: the role of biological nitrification inhibition (BNI)

    PubMed Central

    Subbarao, G. V.; Sahrawat, K. L.; Nakahara, K.; Rao, I. M.; Ishitani, M.; Hash, C. T.; Kishii, M.; Bonnett, D. G.; Berry, W. L.; Lata, J. C.

    2013-01-01

    Background Agriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems. Scope In this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4+)-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and

  13. Soil nitrifying and denitrifying capacities are altered by global change factors in a California annual grassland

    NASA Astrophysics Data System (ADS)

    Niboyet, A.; Le Roux, X.; Barthes, L.; Hungate, B.; Dijkstra, P.; Blankinship, J. C.; Brown, J. R.; Field, C. B.; Leadley, P. W.

    2009-12-01

    Nitrification and denitrification are key mediators of nitrogen (N) cycling, especially N losses, in terrestrial ecosystems, yet little is known about the long-term, in situ responses of these two microbial processes to the simultaneous and interacting global changes likely to occur this century. We investigated the responses of the two steps of nitrification - ammonia oxidation and nitrite oxidation - and of denitrification to the interactive effects of elevated CO2, warming, increased precipitation and N deposition as part of the Jasper Ridge Global Change Experiment. We followed these responses over two growing seasons of the experiment using measures of potential rates of ammonia oxidation, nitrite oxidation, and denitrification, along with key correlates of these activities (gross N mineralization, gross nitrification, soil moisture, soil NH4+ and NO3- concentrations, soil pH, soil temperature, soil CO2 and N2O effluxes, and root and shoot biomass). Across all dates, soil ammonia and nitrite oxidizing capacities responded very differently to global change treatments: soil ammonia oxidizing capacities were increased by 59% in the high N deposition treatment (likely as a result of higher substrate availability for ammonia-oxidizers), while soil nitrite oxidizing capacities did not respond to the N deposition treatment but were reduced by 10% in the increased precipitation treatment. Soil denitrifying capacities were increased by 26% in the high N deposition treatment (likely as a result of higher substrate availability for denitrifiers) and by 15% in the increased precipitation treatment (likely as a result of higher soil water content). Overall, elevated CO2 and warming were found to have little effects on soil nitrifying and denitrifying capacities, and interactive effects between global change components were rare when analyzed across multiple sampling dates. Thus, our results suggest that increased atmospheric N deposition and changes in precipitation

  14. Removal of micropollutants during tertiary wastewater treatment by biofiltration: Role of nitrifiers and removal mechanisms.

    PubMed

    Rattier, M; Reungoat, J; Keller, J; Gernjak, W

    2014-05-01

    The objective of this study was to determine the extent to which a suite of organic micropollutants (MPs) can be removed by biological filtration and the role of bioavailability and ammonia oxidizing microorganisms (AOMs) in the biodegradation process. During approximately one year, laboratory-scale columns with 8 min empty bed contact time (EBCT) and packed with anthracite as filter media were used for treating a tertiary effluent spiked with a broad range of MPs at a target concentration of 2 μg L(-1). In parallel columns, aerobic biomass growth was inhibited by using either the biocide sodium azide (500 mg L(-1) NaN3) or allylthiourea (5 mg L(-1) ATU), specifically inhibiting nitrifying bacteria. Once the biomass had colonized the media, around 15% of the dissolved organic carbon (DOC) contained in the untreated tertiary effluent was removed by non-inhibited columns. The removal of several MPs increased over time indicating the relevance of biological activity for the removal of MPs, while the negative control, the NaN3 inhibited column, showed no significant removal. Out of 33 MPs, 19 were recalcitrant (<25%) to biodegradation under aerobic conditions with the others exhibiting a diverse range of removal efficiency up to 95%. Through inhibition by ATU it was shown that nitrifying bacteria were clearly having a role in the degradation of several MPs, whereas the removal of other MPs was not affected by the presence of the nitrification inhibitor. A relationship between the qualitative assessment of sorption of MPs on granular activated carbon (GAC) and their removal efficiency by biodegradation on anthracite was observed. This result suggested that the affinity of the MPs for GAC media could be a useful indicator of the bioavailability of compounds during biofiltration on anthracite. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Chloraminated Drinking Water Distribution System Nitrification: Batch and Biofilm Inactivation Studies, Model Nitrifying Biofilm Investigations, and Evaluation of Operational Responses to Nitrification Episodes

    EPA Science Inventory

    Studies are currently underway to help fill knowledge gaps that exist in the general understanding of nitrification episodes. One of these gaps includes the need for growth and inactivation kinetic parameters for nitrifiers representative of those inhabiting distribution systems ...

  16. Chloraminated Drinking Water Distribution System Nitrification: Batch and Biofilm Inactivation Studies, Model Nitrifying Biofilm Investigations, and Evaluation of Operational Responses to Nitrification Episodes

    EPA Science Inventory

    Studies are currently underway to help fill knowledge gaps that exist in the general understanding of nitrification episodes. One of these gaps includes the need for growth and inactivation kinetic parameters for nitrifiers representative of those inhabiting distribution systems ...

  17. A comparison of NO and N2O production by the autotrophic nitrifier Nitrosomonas europaea and the heterotrophic nitrifier Alcaligenes faecalis.

    PubMed Central

    Anderson, I C; Poth, M; Homstead, J; Burdige, D

    1993-01-01

    Soil microorganisms are important sources of the nitrogen trace gases NO and N2O for the atmosphere. Present evidence suggests that autotrophic nitrifiers such as Nitrosomonas europaea are the primary producers of NO and N2O in aerobic soils, whereas denitrifiers such as Pseudomonas spp. or Alcaligenes spp. are responsible for most of the NO and N2O emissions from anaerobic soils. It has been shown that Alcaligenes faecalis, a bacterium common in both soil and water, is capable of concomitant heterotrophic nitrification and denitrification. This study was undertaken to determine whether heterotrophic nitrification might be as important a source of NO and N2O as autotrophic nitrification. We compared the responses of N. europaea and A. faecalis to changes in partial O2 pressure (pO2) and to the presence of typical nitrification inhibitors. Maximal production of NO and N2O occurred at low pO2 values in cultures of both N. europaea (pO2, 0.3 kPa) and A. faecalis (pO2, 2 to 4 kPa). With N. europaea most of the NH4+ oxidized was converted to NO2-, with NO and N2O accounting for 2.6 and 1% of the end product, respectively. With A. faecalis maximal production of NO occurred at a pO2 of 2 kPa, and maximal production of N2O occurred at a pO2 of 4 kPa. At these low pO2 values there was net nitrite consumption. Aerobically, A. faecalis produced approximately the same amount of NO but 10-fold more N2O per cell than N. europaea did. Typical nitrification inhibitors were far less effective for reducing emissions of NO and N2O by A. faecalis than for reducing emissions of NO and N2O by N. europaea.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8285659

  18. Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability

    PubMed Central

    Zhu, Xia; Burger, Martin; Doane, Timothy A.; Horwath, William R.

    2013-01-01

    The continuous increase of nitrous oxide (N2O) abundance in the atmosphere is a global concern. Multiple pathways of N2O production occur in soil, but their significance and dependence on oxygen (O2) availability and nitrogen (N) fertilizer source are poorly understood. We examined N2O and nitric oxide (NO) production under 21%, 3%, 1%, 0.5%, and 0% (vol/vol) O2 concentrations following urea or ammonium sulfate [(NH4)2SO4] additions in loam, clay loam, and sandy loam soils that also contained ample nitrate. The contribution of the ammonia (NH3) oxidation pathways (nitrifier nitrification, nitrifier denitrification, and nitrification-coupled denitrification) and heterotrophic denitrification (HD) to N2O production was determined in 36-h incubations in microcosms by 15N-18O isotope and NH3 oxidation inhibition (by 0.01% acetylene) methods. Nitrous oxide and NO production via NH3 oxidation pathways increased as O2 concentrations decreased from 21% to 0.5%. At low (0.5% and 3%) O2 concentrations, nitrifier denitrification contributed between 34% and 66%, and HD between 34% and 50% of total N2O production. Heterotrophic denitrification was responsible for all N2O production at 0% O2. Nitrifier denitrification was the main source of N2O production from ammonical fertilizer under low O2 concentrations with urea producing more N2O than (NH4)2SO4 additions. These findings challenge established thought attributing N2O emissions from soils with high water content to HD due to presumably low O2 availability. Our results imply that management practices that increase soil aeration, e.g., reducing compaction and enhancing soil structure, together with careful selection of fertilizer sources and/or nitrification inhibitors, could decrease N2O production in agricultural soils. PMID:23576736

  19. Effects of pH and Oxygen and Ammonium Concentrations on the Community Structure of Nitrifying Bacteria from Wastewater

    PubMed Central

    Prinčič, Alenka; Mahne, Ivan; Megušar, France; Paul, Eldor A.; Tiedje, James M.

    1998-01-01

    Shifts in nitrifying community structure and function in response to different ammonium concentrations (50, 500, 1,000, and 3,000 mg of N liter−1), pH values (pH 6.0, 7.0, and 8.2), and oxygen concentrations (1, 7, and 21%) were studied in experimental reactors inoculated with nitrifying bacteria from a wastewater treatment plant. The abilities of the communities selected for these conditions to regain their original structures after conditions were returned to the original conditions were also determined. Changes in nitrifying community structure were determined by performing an amplified ribosomal DNA (rDNA) restriction analysis of PCR products obtained with ammonia oxidizer-specific rDNA primers, by phylogenetic probing, by small-subunit (SSU) rDNA sequencing, and by performing a cellular fatty acid analysis. Digestion of ammonia-oxidizer SSU rDNA with five restriction enzymes showed that a high ammonium level resulted in a great community structure change that was reversible once the ammonium concentration was returned to its original level. The smaller changes in community structure brought about by the two pH extremes, however, were irreversible. Sequence analysis revealed that the highest ammonium environment stimulated growth of a nitrifier strain that exhibited 92.6% similarity in a partial SSU rRNA sequence to its nearest relative, Nitrosomonas eutropha C-91, although the PCR product did not hybridize with a general phylogenetic probe for ammonia oxidizers belonging to the β subgroup of the class Proteobacteria. A principal-component analysis of fatty acid methyl ester data detected changes from the starter culture in all communities under the new selective conditions, but after the standard conditions were restored, all communities produced the original fatty acid profiles. PMID:9758771

  20. COMETABOLISM OF CHLORINATED SOLVENTS BY NITRIFYING BACTERIA: KINETICS, SUBSTRATE INTERACTIONS, TOXICITY EFFECTS, AND BACTERIAL RESPONSE. (R825689C013)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  1. COMETABOLISM OF CHLORINATED SOLVENTS BY NITRIFYING BACTERIA: KINETICS, SUBSTRATE INTERACTIONS, TOXICITY EFFECTS, AND BACTERIAL RESPONSE. (R825689C013)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  2. [Effect of Low-concentration Ciprofloxacin on the Nitrification and Nitrifying Microorganisms of Biofilms in Biological Aerated Filter].

    PubMed

    He, Shi; Gu, Chao-chao; Wei, Xin; Huang, Sheng-lin; Liu, Zhen-hong; Xue, Gang; Gao, Pin

    2016-04-15

    Effect of low-concentration ciprofloxacin (CIP) on nitrification and nitrifying microorganisms of biofilms was studied in biological aerated filters (BAF). Quantitative PCR (qPCR) was used to determine the abundance variance of four ciprofloxacin resistance genes (CIP-ARGs) during nitrification in biofilms. The correlations between the abundances of CIP-ARGs and nitrifying microorganisms were also discussed. The results showed that CIP had little influence on the ammonium oxidation process of biofilm microorganisms, whereas inhibition of the nitrite oxidation process was found. The quantitative results of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) including Nitrobacter and Nitrospira indicated that the inhibition on the transformation of nitrite was resulted from the inhibition on Nitrobacter and Nitrospira. In addition, little influence of CIP on the relative abundance of aac and qepA in biofilms was found, but the influence on parC and oqxB was great. The abundance of Nitrotacter exhibited significant positive correlation with the abundance of parC. Similar significant correlation was also found between the abundances of Nitrospira and oqxB. It could be speculated that the genetic elements of different nitrifying microorganisms in biofilms possibly carried CIP-ARGs.

  3. Respirometric response and microbial succession of nitrifying sludge to m-cresol pulses in a sequencing batch reactor.

    PubMed

    Ordaz, Alberto; Sánchez, Mariana; Rivera, Rodrigo; Rojas, Rafael; Zepeda, Alejandro

    2017-02-01

    A nitrifying consortium was kinetically, stoichiometrically and molecularly characterized via the in situ pulse respirometric method and pyrosequencing analysis before and after the addition of m-cresol (25 mg C L(-1)) in a sequencing batch reactor (SBR). Five important kinetic and stoichiometric parameters were determined: the maximum oxygen uptake rate, the maximum nitrification rate, the oxidation yield, the biomass growth yield, and the substrate affinity constant. An inhibitory effect was observed in the nitrification process with a recovery of this by up to eight SBR cycles after m-cresol was added to the system. However, full recovery of the nitrification process was not observed, as the maximum oxygen uptake rate was 25% lower than that of the previous operation without m-cresol addition. Furthermore, the pyrosequencing analyses of the nitrifying consortium after the addition of only two pulses of 25 mg C L(-1) m-cresol showed an important microbial community change represented by a decrease in the nitrifying populations and an increase in the populations degrading phenolic compounds.

  4. Simultaneous ammonium-nitrogen and copper removal, and copper recovery using nitrifying biofilm from the ultra-compact biofilm reactor.

    PubMed

    Lee, L Y; Ong, S L; Ng, H Y; Hu, J Y; Koh, Y N

    2008-09-01

    Simultaneous ammonium-nitrogen (NH(4)(+)-N) and copper removal, and copper recovery in synthetic wastewater using nitrifying biofilm from an ultra-compact biofilm reactor (UCBR) was demonstrated in batch studies, which consisted of three phases: Phase 1 for NH(4)(+)-N and copper removals, Phase 2 for copper recovery, and Phase 3 for NH(4)(+)-N removal. The results showed that more than 96.3% of copper was removed within 60min, while 60.1% of the adsorbed copper was recovered through rinsing the biofilms with 0.1mM of ethylenediaminetetraacetic acid (EDTA). The nitrifying biofilm was able to adsorb 0.245mg of copper/g of biofilms. After recovery treatment, 29.4% of copper remained bound within the nitrifying biofilms. No significant inhibitory effects towards NH(4)(+)-N removal in the presence of 0.92mg copper/L was noted in Phase 1 compared with the control test. However, lower initial pH condition in the recovery process and the accumulation of copper on the biofilm led to 50% inhibition on NH(4)(+)-N removal efficiency in the subsequent phase.

  5. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  6. Application of temperature gradient gel electrophoresis to the characterization of a nitrifying bioaugmentation product.

    PubMed

    Fouratt, Melissa A; Rhodes, Jeremy S; Smithers, Charles M; Love, Nancy G; Stevens, Ann M

    2003-03-01

    The microbial population of a nitrifying bioaugmentation product (NBP) has been examined using a combination of conventional bacteriological methods and modern molecular techniques. Variable region 3 (V3) of the 16S rRNA genes of the bacteria in NBP was amplified via the polymerase chain reaction (PCR) with universal eubacterial primers and analyzed via temperature gradient gel electrophoresis (TGGE). Two of the predominant PCR products in NBP were purified from the TGGE gel matrix, reamplified via PCR and sequenced. Two nitrifying strains (NS500-9 and MPN2) that had been isolated from the NBP mixed consortium and grown in pure culture were found, via TGGE, to have identical 16S rRNA sequences to the PCR products under investigation. Nearly the full-length 16S rRNA genes from these two organisms were PCR-amplified, cloned, and sequenced in order to provide a basis for more accurate phylogenetic analysis. The two dominant organisms in the NBP, NS500-9 and MPN2, were thereby found to be most closely related to Nitrosomonas and Nitrobacter species, respectively, in the database. Samples from a laboratory-scale bioreactor, bioaugmented with NBP, were used in an attempt to correlate an increase in activity with a detectable shift in the population of NS500-9 and MPN2 via TGGE. No detectable shift in population was observed in these samples even though the system exhibited increased levels of nitrification. Therefore, the sensitivity of the TGGE system was also examined by determining the limits of detection when NBP was present in activated sludge. In biomass spiking experiments as well as in genomic DNA spiking experiments, it was found that NBP must be present at a level of at least 5% of the total population in order to be detected, whereas bioaugmentation at 1% of the total population was enough to yield significant improvements in nitrification efficiency. This study demonstrates how community profiling of an undefined microbial population via TGGE can be used to

  7. On mean type aggregation.

    PubMed

    Yager, R R

    1996-01-01

    We introduce and define the concept of mean aggregation of a collection of n numbers. We point out that the lack of associativity of this operation compounds the problem of the extending mean of n numbers to n+1 numbers. The closely related concepts of self identity and the centering property are introduced as one imperative for extending mean aggregation operators. The problem of weighted mean aggregation is studied. A new concept of prioritized mean aggregation is then introduced. We next show that the technique of selecting an element based upon the performance of a random experiment can be considered as a mean aggregation operation.

  8. Nitrification and Autotrophic Nitrifying Bacteria in a Hydrocarbon-Polluted Soil

    PubMed Central

    Deni, Jamal; Penninckx, Michel J.

    1999-01-01

    In vitro ammonia-oxidizing bacteria are capable of oxidizing hydrocarbons incompletely. This transformation is accompanied by competitive inhibition of ammonia monooxygenase, the first key enzyme in nitrification. The effect of hydrocarbon pollution on soil nitrification was examined in situ. In a microcosm study, adding diesel fuel hydrocarbon to an uncontaminated soil (agricultural unfertilized soil) treated with ammonium sulfate dramatically reduced the amount of KCl-extractable nitrate but stimulated ammonium consumption. In a soil with long history of pollution that was treated with ammonium sulfate, 90% of the ammonium was transformed into nitrate after 3 weeks of incubation. Nitrate production was twofold higher in the contaminated soil than in the agricultural soil to which hydrocarbon was not added. To assess if ammonia-oxidizing bacteria acquired resistance to inhibition by hydrocarbon, the contaminated soil was reexposed to diesel fuel. Ammonium consumption was not affected, but nitrate production was 30% lower than nitrate production in the absence of hydrocarbon. The apparent reduction in nitrification resulted from immobilization of ammonium by hydrocarbon-stimulated microbial activity. These results indicated that the hydrocarbon inhibited nitrification in the noncontaminated soil (agricultural soil) and that ammonia-oxidizing bacteria in the polluted soil acquired resistance to inhibition by the hydrocarbon, possibly by increasing the affinity of nitrifying bacteria for ammonium in the soil. PMID:10473409

  9. Removal of triclosan in nitrifying activated sludge: effects of ammonia amendment and bioaugmentation.

    PubMed

    Lee, Do Gyun; Cho, Kun-Ching; Chu, Kung-Hui

    2015-04-01

    This study investigated two possible strategies, increasing ammonia oxidation activity and bioaugmenting with triclosan-degrader Sphingopyxis strain KCY1, to enhance triclosan removal in nitrifying activated sludge (NAS). Triclosan (2 mg L(-1)) was removed within 96-h in NAS bioreactors amended with 5, 25 and 75 mg L(-1) of ammonium (NH4-N). The fastest triclosan removal was observed in 25 mg NH4-NL(-1) amended-bioreactors where high ammonia oxidation occurred. Inhibition of ammonia oxidation and slower triclosan removal were observed in 75 mg NH4-NL(-1) amended-bioreactors. Triclosan removal was correlated to the molar ratio of the amount of nitrate produced to the amount of ammonium removed. Bioaugmentation with strain KCY1 did not enhance triclosan removal in the bioreactors with active ammonia oxidation. Approximately 36-42% and 59% of triclosan added were removed within 24-h by ammonia-oxidizing bacteria and unknown triclosan-degrading heterotrophs, respectively. The results suggested that increasing ammonia oxidation activity can be an effective strategy to enhance triclosan removal in NAS.

  10. Initial and hourly headloss modelling on a tertiary nitrifying wastewater biofiltration plant.

    PubMed

    Bernier, Jean; Rocher, Vincent; Lessard, Paul

    2016-01-01

    The headloss prediction capability of a wastewater biofiltration model is evaluated on data from a full-scale tertiary nitrifying biofilter unit located in the Paris conurbation (Achères, France; 6,000,000 population equivalent). The model has been previously calibrated on nutrient conversion and TSS filtration observations. In this paper the mass of extracted biofilm during biofilter backwash and the headloss value at the start of an operation cycle are first calibrated on sludge production estimations and relative pressure measurements over the year 2009. The calibrated model is then used on two one-month periods in 2012 for which hourly headloss measurements were acquired. The observed trends are correctly predicted for 2009 but the model exhibits some heavy daily variation that is not found in measurements. Hourly predictions stay close to observations, although the model error rises slightly when the headloss does not vary much. The global model shows that both nutrient conversion and headloss build-up can be reasonably well predicted at the same time on a full-scale plant.

  11. Application of high rate nitrifying trickling filters for potable water treatment.

    PubMed

    van den Akker, Ben; Holmes, Mike; Cromar, Nancy; Fallowfield, Howard

    2008-11-01

    The interference of ammonia with chlorination is a prevalent problem encountered by water treatment plants located throughout South East Asia. The efficacy of high rate, plastic-packed trickling filters as a pre-treatment process to remove low concentrations of ammonia from polluted surface water was investigated. This paper presents the findings from a series of pilot experiments, which were designed to investigate the effect of specific conditions-namely low ammonia feed concentrations (0.5-5.0 mg NH(4)-NL(-1)), variations in hydraulic surface load (72.5-145 m(3)m(-2)d(-1)) and high suspended solid loads (51+/-25 mgL(-1))-on filter nitrifying capacity. The distribution of nitrification activity throughout a trickling filter bed was also characterised. Results confirmed that high hydraulic rate trickling filters were able to operate successfully, under ammonia-N concentrations some 10- to 50-fold lower and at hydraulic loading rates 30-100 times greater than those of conventional wastewater applications. Mass transport limitations posed by low ammonia-N concentrations on overall filter performance were insignificant, where apparent nitrification rates (0.4-1.6 g NH(4)-Nm(-2)d(-1)), equivalent to that of wastewater filters were recorded. High inert suspended solid loadings had no adverse effect on nitrification. Results imply that implementation of high rate trickling filters at the front-end of a water treatment train would reduce the ammonia-related chlorine demand, thereby offering significant cost savings.

  12. Predicting N2O emissions from nitrifying and denitrifying biofilms: a modeling study.

    PubMed

    Sabba, Fabrizio; Picioreanu, Cristian; Boltz, Joshua P; Nerenberg, Robert

    2017-02-01

    Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas. While our understanding of N2O emissions from suspended-growth processes has advanced significantly, less is known about emissions from biofilm processes. Biofilms may behave differently due to their substrate gradients and microbial stratification. In this study, we used mathematical modeling to explore the mechanisms of N2O emissions from nitrifying and denitrifying biofilms. Our ammonia-oxidizing bacteria biofilm model suggests that N2O emissions from biofilm can be significantly greater than from suspended-growth systems. The driving factor is the diffusion of hydroxylamine, a nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. The presence of nitrite-oxidizing bacteria further increased emissions. For denitrifying biofilms, our results suggest that emissions are generally greater than for suspended-growth systems. However, the magnitude of the difference depends on the bulk dissolved oxygen, chemical oxygen demand, and nitrate concentrations, as well as the biofilm thickness. Overall, the accumulation and diffusion of key intermediates, i.e. hydroxylamine and nitrite, distinguish biofilms from suspended-growth systems. Our research suggests that the mechanisms of N2O emissions from biofilms are much more complex than suspended-growth systems, and that emissions may be higher in many cases.

  13. Free chlorine and monochloramine application to nitrifying biofilm: comparison of biofilm penetration, activity, and viability.

    PubMed

    Lee, Woo Hyoung; Wahman, David G; Bishop, Paul L; Pressman, Jonathan G

    2011-02-15

    Biofilm in drinking water systems is undesirable. Free chlorine and monochloramine are commonly used as secondary drinking water disinfectants, but monochloramine is perceived to penetrate biofilm better than free chlorine. However, this hypothesis remains unconfirmed by direct biofilm monochloramine measurement. This study compared free chlorine and monochloramine biofilm penetration into an undefined mixed-culture nitrifying biofilm by use of microelectrodes and assessed the subsequent effect on biofilm activity and viability by use of dissolved oxygen (DO) microelectrodes and confocal laser scanning microscopy (CLSM) with LIVE/DEAD BacLight. For equivalent chlorine concentrations, monochloramine initially penetrated biofilm 170 times faster than free chlorine, and even after subsequent application to a monochloramine penetrated biofilm, free chlorine penetration was limited. DO profiles paralleled monochloramine profiles, providing evidence that either the biofilm was inactivated with monochloramine's penetration or its persistence reduced available substrate (free ammonia). While this research clearly demonstrated monochloramine's greater penetration, this penetration did not necessarily translate to immediate viability loss. Even though free chlorine's penetration was limited compared to that of monochloramine, it more effectively (on a cell membrane integrity basis) inactivated microorganisms near the biofilm surface. Limited free chlorine penetration has implications when converting to free chlorine in full-scale chloraminated systems in response to nitrification episodes.

  14. Measuring and modeling the oxygen profile in a nitrifying Moving Bed Biofilm Reactor.

    PubMed

    Masić, Alma; Bengtsson, Jessica; Christensson, Magnus

    2010-09-01

    In this paper we determine the oxygen profile in a biofilm on suspended carriers in two ways: firstly by microelectrode measurements and secondly by a simple mathematical model. The Moving Bed Biofilm Reactor is well-established for wastewater treatment where bacteria grow as a biofilm on the protective surfaces of suspended carriers. The flat shaped BiofilmChip P was developed to allow good conditions for transport of substrates into the biofilm. The oxygen profile was measured in situ the nitrifying biofilm with a microelectrode and it was simulated with a one-dimensional mathematical model. We extended the model by adding a CSTR equation, to connect the reactor to the biofilm through the boundary conditions. We showed the dependence of the thickness of the mass transfer boundary layer on the bulk flow rate. Finally, we estimated the erosion parameter lambda to increase the concordance between the measured and simulated profiles. This lead to a simple empirical relationship between lambda and the flow rate. The data gathered by in situ microelectrode measurements can, together with the mathematical model, be used in predictive modeling and give more insight in the design of new carriers, with the ambition of making process operation more energy efficient. Copyright 2010 Elsevier Inc. All rights reserved.

  15. A new process for enriching nitrifiers in activated sludge through separate heterotrophic wasting from biofilm carriers.

    PubMed

    Parker, Denny S; Rusten, Bjørn; Wien, Asgeir; Siljudalen, Jon G

    2002-01-01

    A new process, the biofilm-activated sludge innovative nitrification (BASIN) process, consisting of a moving-bed biofilm reactor (MBBR) with separate heterotrophic wasting, followed by an activated-sludge process, has been proposed to reduce the volumetric requirements of the activated-sludge process for nitrification. The basic principle is to remove chemical oxygen demand on the biofilm carriers by heterotrophic organisms and then to waste a portion of the heterotrophic biomass before it can be released into the activated-sludge reactor. By this means, the amount of heterotrophic organisms grown in the activated-sludge reactor is reduced, thereby reducing the volume of that tank needed for nitrification. For nitrification applications, the simplest method for stripping biomass was to use an in-tank technique using high shearing rates with aeration. Bench-scale testing showed sludge yields in the BASIN process were one-half of that in a control activated-sludge process and twice that of a process line with intermediate settling between the MBBR and activated-sludge stage. Critical washout solids retention times for nitrifiers were the same for all three lines, so activated-sludge volumes for the BASIN process could be reduced by 50% compared with the control. Originally conceived process concepts for the BASIN process were confirmed by the experimental work.

  16. Performance of a pilot-scale nitrifying trickling filter treating municipal aerated lagoon effluent.

    PubMed

    Coats, Erik R; Watson, Ben; Lee, Kiersten; Hammer, Matt

    2015-01-01

    Colfax, WA, operates an aerated lagoon to achieve compliance with its National Pollutant Discharge Elimination System (NPDES) permit, which currently requires biochemical oxygen demand (BOD) and total suspended solids (TSS) removal. However, ammonia removal may soon be required, and Colfax is considering a nitrifying trickling filter (NTF) that would allow them to also maintain the lagoons. To obtain data from which to ultimately design a full-scale system, a four-year NTF pilot study was performed. Results demonstrated that an NTF would be an effective, reliable NH3 removal method and could produce effluent NH3 concentrations < 1.0 mg/L. NTF performance was characterized by zero- and first-order kinetics; zero-order rates correlated with influent NH3 concentrations and mass load. Utilizing data from these investigations it was determined that the pilot NTF could be reduced by 19%, which demonstrates the value of pilot testing. Finally, pilot data was evaluated to provide a data set that will be useful to engineers designing full-scale NTFs.

  17. Attempts to improve nitrogen utilization efficiency of aquaponics through nitrifies addition and filler gradation.

    PubMed

    Zou, Yina; Hu, Zhen; Zhang, Jian; Xie, Huijun; Liang, Shuang; Wang, Jinhe; Yan, Runxin

    2016-04-01

    Aquaponics has attracted worldwide attention in recent years and is considered as an alternative technology for conventional aquaculture. In this study, common carp (Cyprinus carpio) and pakchoi (Brassica chinensis) were cultured in lab-scale aquaponics, and attempts were conducted to enhance its nitrogen utilization efficiency (NUE) through two optimization methods, i.e., nitrifies addition (NA) and filler gradation (FG). Results showed that NA and FG could improve the NUE of aquaponics by 8.8 and 16.0%, respectively, compared with control. The total ammonia (TAN) and nitrite (NO2(-)) concentrations in NA and FG systems were maintained at relatively low level (TAN < 0.5 mg/L, NO2(-) < 0.1 mg/L), which demonstrated that both the NA and FG could provide non-toxic water environment for fish culture. Nitrous oxide conversion ratio of the control, NA, and FG were 0.8, 1.2, and 1.7%, respectively, indicating that media-based aquaponics also contributed to global warming. Although the two proposed attempts in this study caused more N2O emission, they made new breakthrough in improving the NUE of aquaponics.

  18. Physiological and transcriptional responses of nitrifying bacteria exposed to copper in activated sludge.

    PubMed

    Ouyang, Fan; Zhai, Hongyan; Ji, Min; Zhang, Hongyang; Dong, Zhao

    2016-01-15

    Cu inhibition of gene transcription in ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were rarely studied simultaneously in activated sludge. In this study, the transcription of amoA (for AOB) and nxrB (for NOB), nitrification efficiencies, AOB and NOB respiratory rates, and Cu distribution were simultaneously investigated. Modeling the relationships among the aforementioned parameters revealed that in complex activated sludge systems, nitrification efficiency was an insensitive parameter for showing Cu inhibition. Respiration activities and gene transcription were sensitive to Cu and positively correlated with each other. The transcription of amoA and nxrB genes indicated that the Cu had different inhibitory effects on AOB and NOB. AOB were more susceptible to Cu toxicity than NOB. Moreover, the degree of Cu inhibition on ammonia oxidation was greater than on nitrite oxidation. The analysis and related modeling results indicate that the inhibitory actions of Cu on nitrifying bacteria could mainly be attributed to intracellular Cu. The findings from this study provide insight into the mechanism of Cu inhibition on nitrification in complex activated sludge systems.

  19. Combined molecular and conventional analyses of nitrifying bacterium diversity in activated sludge: Nitrosococcus mobilis and Nitrospira-like bacteria as dominant populations.

    PubMed

    Juretschko, S; Timmermann, G; Schmid, M; Schleifer, K H; Pommerening-Röser, A; Koops, H P; Wagner, M

    1998-08-01

    The ammonia-oxidizing and nitrite-oxidizing bacterial populations occurring in the nitrifying activated sludge of an industrial wastewater treatment plant receiving sewage with high ammonia concentrations were studied by use of a polyphasic approach. In situ hybridization with a set of hierarchical 16S rRNA-targeted probes for ammonia-oxidizing bacteria revealed the dominance of Nitrosococcus mobilis-like bacteria. The phylogenetic affiliation suggested by fluorescent in situ hybridization (FISH) was confirmed by isolation of N. mobilis as the numerically dominant ammonia oxidizer and subsequent comparative 16S rRNA gene (rDNA) sequence and DNA-DNA hybridization analyses. For molecular fine-scale analysis of the ammonia-oxidizing population, a partial stretch of the gene encoding the active-site polypeptide of ammonia monooxygenase (amoA) was amplified from total DNA extracted from ammonia oxidizer isolates and from activated sludge. However, comparative sequence analysis of 13 amoA clone sequences from activated sludge demonstrated that these sequences were highly similar to each other and to the corresponding amoA gene fragments of Nitrosomonas europaea Nm50 and the N. mobilis isolate. The unexpected high sequence similarity between the amoA gene fragments of the N. mobilis isolate and N. europaea indicates a possible lateral gene transfer event. Although a Nitrobacter strain was isolated, members of the nitrite-oxidizing genus Nitrobacter were not detectable in the activated sludge by in situ hybridization. Therefore, we used the rRNA approach to investigate the abundance of other well-known nitrite-oxidizing bacterial genera. Three different methods were used for DNA extraction from the activated sludge. For each DNA preparation, almost full-length genes encoding small-subunit rRNA were separately amplified and used to generate three 16S rDNA libraries. By comparative sequence analysis, 2 of 60 randomly selected clones could be assigned to the nitrite

  20. Combined Molecular and Conventional Analyses of Nitrifying Bacterium Diversity in Activated Sludge: Nitrosococcus mobilis and Nitrospira-Like Bacteria as Dominant Populations

    PubMed Central

    Juretschko, Stefan; Timmermann, Gabriele; Schmid, Markus; Schleifer, Karl-Heinz; Pommerening-Röser, Andreas; Koops, Hans-Peter; Wagner, Michael

    1998-01-01

    The ammonia-oxidizing and nitrite-oxidizing bacterial populations occurring in the nitrifying activated sludge of an industrial wastewater treatment plant receiving sewage with high ammonia concentrations were studied by use of a polyphasic approach. In situ hybridization with a set of hierarchical 16S rRNA-targeted probes for ammonia-oxidizing bacteria revealed the dominance of Nitrosococcus mobilis-like bacteria. The phylogenetic affiliation suggested by fluorescent in situ hybridization (FISH) was confirmed by isolation of N. mobilis as the numerically dominant ammonia oxidizer and subsequent comparative 16S rRNA gene (rDNA) sequence and DNA-DNA hybridization analyses. For molecular fine-scale analysis of the ammonia-oxidizing population, a partial stretch of the gene encoding the active-site polypeptide of ammonia monooxygenase (amoA) was amplified from total DNA extracted from ammonia oxidizer isolates and from activated sludge. However, comparative sequence analysis of 13 amoA clone sequences from activated sludge demonstrated that these sequences were highly similar to each other and to the corresponding amoA gene fragments of Nitrosomonas europaea Nm50 and the N. mobilis isolate. The unexpected high sequence similarity between the amoA gene fragments of the N. mobilis isolate and N. europaea indicates a possible lateral gene transfer event. Although a Nitrobacter strain was isolated, members of the nitrite-oxidizing genus Nitrobacter were not detectable in the activated sludge by in situ hybridization. Therefore, we used the rRNA approach to investigate the abundance of other well-known nitrite-oxidizing bacterial genera. Three different methods were used for DNA extraction from the activated sludge. For each DNA preparation, almost full-length genes encoding small-subunit rRNA were separately amplified and used to generate three 16S rDNA libraries. By comparative sequence analysis, 2 of 60 randomly selected clones could be assigned to the nitrite

  1. Bacterial Vaginosis

    MedlinePlus

    ... Form Controls Cancel Submit Search the CDC Bacterial Vaginosis (BV) Note: Javascript is disabled or is not ... STD on Facebook Sexually Transmitted Diseases (STDs) Bacterial Vaginosis – CDC Fact Sheet Language: English (US) Españ ...

  2. Effects of Cr(III) and CR(VI) on nitrification inhibition as determined by SOUR, function-specific gene expression and 16S rRNA sequence analysis of wastewater nitrifying enrichments

    EPA Science Inventory

    The effect of Cr(III) and Cr(VI) on ammonia oxidation, the transcriptional responses of functional genes involved in nitrification and changes in 16S rRNA level sequences were examined in nitrifying enrichment cultures. The nitrifying bioreactor was operated as a continuous react...

  3. Effects of Cr(III) and CR(VI) on nitrification inhibition as determined by SOUR, function-specific gene expression and 16S rRNA sequence analysis of wastewater nitrifying enrichments

    EPA Science Inventory

    The effect of Cr(III) and Cr(VI) on ammonia oxidation, the transcriptional responses of functional genes involved in nitrification and changes in 16S rRNA level sequences were examined in nitrifying enrichment cultures. The nitrifying bioreactor was operated as a continuous react...

  4. Contributions of autotrophic and heterotrophic nitrifiers to soil NO and N sub 2 O emissions

    SciTech Connect

    Tortoso, A.C.; Hutchinson, G.L. )

    1990-06-01

    Soil emission of gaseous N oxides during nitrification of ammonium represents loss of an available plant nutrient and has an important impact on the chemistry of the atmosphere. We used selective inhibitors and a glucose amendment in a factorial design to determine the relative contributions of autotrophic ammonium oxidizers, autotrophic nitrite oxidizers, and heterotrophic nitrifiers to nitric oxide (NO) and nitrous oxide (N{sub 2}O) emissions from aerobically incubated soil following the addition of 160 mg of N as ammonium sulfate kg{sup {minus}1}. Without added C, peak NO emissions of 4 {mu}g of N kg{sup {minus}1}h{sup {minus}1} were increased to 15 {mu}g of N kg{sup {minus}1} h{sup {minus}1} by the addition of sodium chlorate, a nitrite oxidation inhibitor, but were reduced to 0.01 {mu}g of N kg{sup {minus}1} h{sup {minus}1} in the presence of nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine), an inhibitor of autotrophic ammonium oxidation. Carbon-amended soils had somewhat higher NO emission rates from these three treatments (6, 18, and 0.1 {mu}g of N kg{sup {minus}1} h{sup {minus}1} after treatment with glucose, sodium chlorate, or nitrapyrin, respectively) until the glucose was exhausted but lower rates during the remainder of the incubation. Nitrous oxide emission levels exhibited trends similar to those observed for NO but were about 20 times lower. Periodic soil chemical analyses showed no increase in the nitrate concentration of soil treated with sodium chlorate until after the period of peak NO and N{sub 2}O emissions; the nitrate concentration of soil treated with nitrapyrin remained unchanged throughout the incubation. These results suggest that chemoautotrophic ammonium-oxidizing bacteria are the predominant source of NO and N{sub 2}O produced during nitrification in soil.

  5. Ecology of Nitrogen Fixing, Nitrifying, and Denitrifying Microorganisms in Tropical Forest Soils

    PubMed Central

    Pajares, Silvia; Bohannan, Brendan J. M.

    2016-01-01

    Soil microorganisms play important roles in nitrogen cycling within forest ecosystems. Current research has revealed that a wider variety of microorganisms, with unexpected diversity in their functions and phylogenies, are involved in the nitrogen cycle than previously thought, including nitrogen-fixing bacteria, ammonia-oxidizing bacteria and archaea, heterotrophic nitrifying microorganisms, and anammox bacteria, as well as denitrifying bacteria, archaea, and fungi. However, the vast majority of this research has been focused in temperate regions, and relatively little is known regarding the ecology of nitrogen-cycling microorganisms within tropical and subtropical ecosystems. Tropical forests are characterized by relatively high precipitation, low annual temperature fluctuation, high heterogeneity in plant diversity, large amounts of plant litter, and unique soil chemistry. For these reasons, regulation of the nitrogen cycle in tropical forests may be very different from that of temperate ecosystems. This is of great importance because of growing concerns regarding the effect of land use change and chronic-elevated nitrogen deposition on nitrogen-cycling processes in tropical forests. In the context of global change, it is crucial to understand how environmental factors and land use changes in tropical ecosystems influence the composition, abundance and activity of key players in the nitrogen cycle. In this review, we synthesize the limited currently available information regarding the microbial communities involved in nitrogen fixation, nitrification and denitrification, to provide deeper insight into the mechanisms regulating nitrogen cycling in tropical forest ecosystems. We also highlight the large gaps in our understanding of microbially mediated nitrogen processes in tropical forest soils and identify important areas for future research. PMID:27468277

  6. Biofilm Thickness Influences Biodiversity in Nitrifying MBBRs-Implications on Micropollutant Removal.

    PubMed

    Torresi, Elena; Fowler, S Jane; Polesel, Fabio; Bester, Kai; Andersen, Henrik R; Smets, Barth F; Plósz, Benedek Gy; Christensson, Magnus

    2016-09-06

    In biofilm systems for wastewater treatment (e.g., moving bed biofilms reactors-MBBRs) biofilm thickness is typically not under direct control. Nevertheless, biofilm thickness is likely to have a profound effect on the microbial diversity and activity, as a result of diffusion limitation and thus substrate penetration in the biofilm. In this study, we investigated the impact of biofilm thickness on nitrification and on the removal of more than 20 organic micropollutants in laboratory-scale nitrifying MBBRs. We used novel carriers (Z-carriers, AnoxKaldnes) that allowed controlling biofilm thickness at 50, 200, 300, 400, and 500 μm. The impact of biofilm thickness on microbial community was assessed via 16S rRNA gene amplicon sequencing and ammonia monooxygenase (amoA) abundance quantification through quantitative PCR (qPCR). Results from batch experiments and microbial analysis showed that (i) the thickest biofilm (500 μm) presented the highest specific biotransformation rate constants (kbio, L g(-1) d(-1)) for 14 out of 22 micropollutants; (ii) biofilm thickness positively associated with biodiversity, which was suggested as the main factor for the observed enhancement of kbio; (iii) the thinnest biofilm (50 μm) exhibited the highest nitrification rate (gN d(-1) g(-1)), amoA gene abundance and kbio values for some of the most recalcitrant micropollutants (i.e., diclofenac and targeted sulfonamides). Although thin biofilms favored nitrification activity and the removal of some micropollutants, treatment systems based on thicker biofilms should be considered to enhance the elimination of a broad spectrum of micropollutants.

  7. Contributions of Autotrophic and Heterotrophic Nitrifiers to Soil NO and N2O Emissions †

    PubMed Central

    Tortoso, A. C.; Hutchinson, G. L.

    1990-01-01

    Soil emission of gaseous N oxides during nitrification of ammonium represents loss of an available plant nutrient and has an important impact on the chemistry of the atmosphere. We used selective inhibitors and a glucose amendment in a factorial design to determine the relative contributions of autotrophic ammonium oxidizers, autotrophic nitrite oxidizers, and heterotrophic nitrifiers to nitric oxide (NO) and nitrous oxide (N2O) emissions from aerobically incubated soil following the addition of 160 mg of N as ammonium sulfate kg−1. Without added C, peak NO emissions of 4 μg of N kg−1 h−1 were increased to 15 μg of N kg−1 h−1 by the addition of sodium chlorate, a nitrite oxidation inhibitor, but were reduced to 0.01 μg of N kg−1 h−1 in the presence of nitrapyrin [2-chloro-6-(trichloromethyl)-pyridine], an inhibitor of autotrophic ammonium oxidation. Carbon-amended soils had somewhat higher NO emission rates from these three treatments (6, 18, and 0.1 μg of N kg−1 h−1 after treatment with glucose, sodium chlorate, or nitrapyrin, respectively) until the glucose was exhausted but lower rates during the remainder of the incubation. Nitrous oxide emission levels exhibited trends similar to those observed for NO but were about 20 times lower. Periodic soil chemical analyses showed no increase in the nitrate concentration of soil treated with sodium chlorate until after the period of peak NO and N2O emissions; the nitrate concentration of soil treated with nitrapyrin remained unchanged throughout the incubation. These results suggest that chemoautotrophic ammonium-oxidizing bacteria are the predominant source of NO and N2O produced during nitrification in soil. PMID:16348220

  8. Community structure and in situ activity of nitrifying bacteria in Phragmites root-associated biofilms.

    PubMed

    Okabe, Satoshi; Nakamura, Yoshiyuki; Satoh, Hisashi

    2012-01-01

    The amount of oxygen released by Phragmites roots and the community structure and in situ activity of nitrifying bacteria in the root biofilms were analyzed by the combined use of 16S rRNA gene-cloning analysis, quantitative PCR (qPCR) assay and microelectrodes. Axial and radial O₂ microprofiles were obtained for individual roots of Phragmites in a horizontal flow reactor fed with artificial medium continuously. Axial O₂ profiles revealed that O₂ was released at a rate of 0.21 μmol O₂ cm⁻² (root surface area) h⁻¹ only in the apical region (up to ca. 40 mm from the root apex), where there was a high abundance (10⁷ to 10⁸ copies g⁻¹ biomass) of Nitrosomonas-like AOB and Nitrospira-like NOB. This abundance, however, sharply declined to the detection limit at positions more basal than 80 mm. Phylogenetic analysis based on 16S rRNA gene identified strains related to Nitrosomonas oligotropha and Nitrosomonas cryotolerans as the predominant AOB and strains related to Nitrospira marina and Nitrospira moscoviensis as the predominant NOB in the root biofilms. Based on radial O₂ microprofiles, the oxic region only extended about 0.5 mm into the surrounding sediment due to a high rate of O₂ consumption in the rhizosphere. The net NH₄⁺ and O₂ consumption rates in the apical region were higher than those determined at the oxic sediment surface in which the abundance of AOB and NOB was one order of magnitude lower than in the rhizosphere. These results clearly indicated that Phragmites root biofilms played an important role in nitrification in the waterlogged anoxic sediment.

  9. Ecology of Nitrogen Fixing, Nitrifying, and Denitrifying Microorganisms in Tropical Forest Soils.

    PubMed

    Pajares, Silvia; Bohannan, Brendan J M

    2016-01-01

    Soil microorganisms play important roles in nitrogen cycling within forest ecosystems. Current research has revealed that a wider variety of microorganisms, with unexpected diversity in their functions and phylogenies, are involved in the nitrogen cycle than previously thought, including nitrogen-fixing bacteria, ammonia-oxidizing bacteria and archaea, heterotrophic nitrifying microorganisms, and anammox bacteria, as well as denitrifying bacteria, archaea, and fungi. However, the vast majority of this research has been focused in temperate regions, and relatively little is known regarding the ecology of nitrogen-cycling microorganisms within tropical and subtropical ecosystems. Tropical forests are characterized by relatively high precipitation, low annual temperature fluctuation, high heterogeneity in plant diversity, large amounts of plant litter, and unique soil chemistry. For these reasons, regulation of the nitrogen cycle in tropical forests may be very different from that of temperate ecosystems. This is of great importance because of growing concerns regarding the effect of land use change and chronic-elevated nitrogen deposition on nitrogen-cycling processes in tropical forests. In the context of global change, it is crucial to understand how environmental factors and land use changes in tropical ecosystems influence the composition, abundance and activity of key players in the nitrogen cycle. In this review, we synthesize the limited currently available information regarding the microbial communities involved in nitrogen fixation, nitrification and denitrification, to provide deeper insight into the mechanisms regulating nitrogen cycling in tropical forest ecosystems. We also highlight the large gaps in our understanding of microbially mediated nitrogen processes in tropical forest soils and identify important areas for future research.

  10. Dynamics of viable nitrifier community, N-mineralization and nitrification in seasonally dry tropical forests and savanna.

    PubMed

    Singh, J S; Kashyap, A K

    2006-01-01

    The study was conducted in Vindhyan region, to assess the N-mineralization, nitrification and size of viable community of ammonium- and nitrite-oxidizing bacteria as affected by different sites and seasons. Six different ecosystems (four forests and two savannas), which differ in terms of topography, vegetation and moisture status, were selected for the present study. The soils of the study sites differ significantly in its physico-chemical properties. The savanna site had significantly higher pH (7.2), bulk density (1.37 g cm(-3)) and silt content (67.80%) but lower water holding capacity (1.37%), total-C (16,356 microg g(-1) dry soil), N (1090 microg g(-1) dry soil) and P (213 microg g(-1) dry soil) than forest sites. The soil moisture content, N-mineralization, nitrification rates and numbers of ammonium- and nitrite-oxidizing bacteria were highest in the wet season and lowest in dry season, while the size of mineral-N (NH4(+)-N and NO3(-)-N) showed a reverse trend at the sites. The N-mineralization, nitrification and nitrifier population size differ significantly across the site and season. The numbers of free-living cells of ammonium- and nitrite-oxidizing bacteria were significantly related to each other and to N-mineralization, nitrification, soil moisture and mineral-N components. The N-mineralization, nitrification and the viable number of nitrifying cells were consistently higher for forest soils compared to savanna sites. It was concluded that soil microbial process (N-mineralization and nitrification) and nitrifier population size were dependent on site topography, vegetation cover and soil moisture status.

  11. Effect of Algal Inoculation on COD and Nitrogen Removal, and Indigenous Bacterial Dynamics in Municipal Wastewater.

    PubMed

    Lee, Jangho; Lee, Jaejin; Shukla, Sudheer Kumar; Park, Joonhong; Lee, Tae Kwon

    2016-05-28

    The effects of algal inoculation on chemical oxygen demand (COD) and total nitrogen (TN) removal, and indigenous bacterial dynamics were investigated in municipal wastewater. Experiments were conducted with municipal wastewater inoculated with either Chlorella vulgaris AG10032, Selenastrum gracile UTEX 325, or Scenedesmus quadricauda AG 10308. C. vulgaris and S. gracile as fast growing algae in municipal wastewater, performed high COD and TN removal in contrast to Sc. quadricauda. The indigenous bacterial dynamics revealed by 16S rRNA gene amplification showed different bacterial shifts in response to different algal inoculations. The dominant bacterial genera of either algal case were characterized as heterotrophic nitrifying bacteria. Our results suggest that selection of indigenous bacteria that symbiotically interact with algal species is important for better performance of wastewater treatment.

  12. The response of nitrifying microbial assemblages to ammonium (NH4+) enrichment from salmon farm activities in a northern Chilean Fjord

    NASA Astrophysics Data System (ADS)

    Elizondo-Patrone, Claudia; Hernández, Klaudia; Yannicelli, Beatriz; Olsen, Lasse Mork; Molina, Verónica

    2015-12-01

    The consequences of aquaculture include alterations in nitrogen cycling in aquatic environments that may lead to ecosystem degradation. Herein salmon aquaculture release of ammonium (NH4+) to the water column and its effects on natural archaea and bacteria ammonia-oxidizers (AOA and AOB) and nitrite-oxidizing bacteria (NOB) community structure were studied in the Comau fjord using molecular approaches, such as: cloning (AOA and AOB richness), qPCR for C. Nitrosopumilus maritimus (AOA) and Nitrospina sp. (NOB) abundance (DNA) and RT-qPCR only for Nitrospina sp activity (RNA). Sampling was carried out in brackish (0.7-25 salinity, <5 m depth) and marine (>30 salinity, 25 m depth) waters during contrasting salmon production periods: rest (winter 2012), growth and harvest (summer and winter 2013). During the rest period, the highest NH4+ concentration was observed at Vodudahue River, whereas during productive periods NH4+ accumulated in the brackish layer inside salmon cages and in the vicinty (up to 700 m distance from the cages). The nitrifier community from the fjord reference station (Stn-C) was characterized by C. N. maritimus (AOA) and Nitrosomonas sp. (AOB) sequences affiliated with cosmopolitan ecotypes (e.g., marine, freshwater, hydrothermal), maxima abundances of C. N. maritimus (AOA) and Nitrospina sp. and extreme ranges of Nitrospina sp. activity occurred in the brackish layer. During productive periods, abundances of C. N. maritimus were co-varied with NH4+ concentrations inside salmon cages (summer) and the adjacent areas (winter). Productive periods were characterized by lower abundances but more homogeneity between brackish and marine areas than for the Stn-C nitrifiers. The physiological state of Nitrospina sp. estimated from cDNA:DNA ratios indicated higher growth during winter 2013 associated with NH4+ enrichment derived from production and river input. Our results suggest that in Comau Fjord, NH4+ enrichment events occur during salmon production and

  13. Bacterial Sialidase

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

  14. Bacterial Sialidase

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

  15. Diatom-associated bacteria are required for aggregation of Thalassiosira weissflogii

    PubMed Central

    Gärdes, Astrid; Iversen, Morten H; Grossart, Hans-Peter; Passow, Uta; Ullrich, Matthias S

    2011-01-01

    Aggregation of algae, mainly diatoms, is an important process in marine systems leading to the settling of particulate organic carbon predominantly in the form of marine snow. Exudation products of phytoplankton form transparent exopolymer particles (TEP), which acts as the glue for particle aggregation. Heterotrophic bacteria interacting with phytoplankton may influence TEP formation and phytoplankton aggregation. This bacterial impact has not been explored in detail. We hypothesized that bacteria attaching to Thalassiosira weissflogii might interact in a yet-to-be determined manner, which could impact TEP formation and aggregate abundance. The role of individual T. weissflogii-attaching and free-living new bacterial isolates for TEP production and diatom aggregation was investigated in vitro. T. weissflogii did not aggregate in axenic culture, and striking differences in aggregation dynamics and TEP abundance were observed when diatom cultures were inoculated with either diatom-attaching or free-living bacteria. The data indicated that free-living bacteria might not influence aggregation whereas bacteria attaching to diatom cells may increase aggregate formation. Interestingly, photosynthetically inactivated T. weissflogii cells did not aggregate regardless of the presence of bacteria. Comparison of aggregate formation, TEP production, aggregate sinking velocity and solid hydrated density revealed remarkable differences. Both, photosynthetically active T. weissflogii and specific diatom-attaching bacteria were required for aggregation. It was concluded that interactions between heterotrophic bacteria and diatoms increased aggregate formation and particle sinking and thus may enhance the efficiency of the biological pump. PMID:20827289

  16. Gut bacteria mediate aggregation in the German cockroach.

    PubMed

    Wada-Katsumata, Ayako; Zurek, Ludek; Nalyanya, Godfrey; Roelofs, Wendell L; Zhang, Aijun; Schal, Coby

    2015-12-22

    Aggregation of the German cockroach, Blattella germanica, is regulated by fecal aggregation agents (pheromones), including volatile carboxylic acids (VCAs). We demonstrate that the gut microbial community contributes to production of these semiochemicals. Chemical analysis of the fecal extract of B. germanica revealed 40 VCAs. Feces from axenic cockroaches (no microorganisms in the alimentary tract) lacked 12 major fecal VCAs, and 24 of the remaining compounds were represented at extremely low amounts. Olfactory and aggregation bioassays demonstrated that nymphs strongly preferred the extract of control feces over the fecal extract of axenic cockroaches. Additionally, nymphs preferred a synthetic blend of 6 fecal VCAs over a solvent control or a previously identified VCA blend. To test whether gut bacteria contribute to the production of fecal aggregation agents, fecal aerobic bacteria were cultured, isolated, and identified. Inoculation of axenic cockroaches with individual bacterial taxa significantly rescued the aggregation response to the fecal extract, and inoculation with a mix of six bacterial isolates was more effective than with single isolates. The results indicate that the commensal gut microbiota contributes to production of VCAs that act as fecal aggregation agents and that cockroaches discriminate among the complex odors that emanate from a diverse microbial community. Our results highlight the pivotal role of gut bacteria in mediating insect-insect communication. Moreover, because the gut microbial community reflects the local environment, local plasticity in fecal aggregation pheromones enables colony-specific odors and fidelity to persistent aggregation sites.

  17. Gut bacteria mediate aggregation in the German cockroach

    PubMed Central

    Wada-Katsumata, Ayako; Zurek, Ludek; Nalyanya, Godfrey; Roelofs, Wendell L.; Zhang, Aijun; Schal, Coby

    2015-01-01

    Aggregation of the German cockroach, Blattella germanica, is regulated by fecal aggregation agents (pheromones), including volatile carboxylic acids (VCAs). We demonstrate that the gut microbial community contributes to production of these semiochemicals. Chemical analysis of the fecal extract of B. germanica revealed 40 VCAs. Feces from axenic cockroaches (no microorganisms in the alimentary tract) lacked 12 major fecal VCAs, and 24 of the remaining compounds were represented at extremely low amounts. Olfactory and aggregation bioassays demonstrated that nymphs strongly preferred the extract of control feces over the fecal extract of axenic cockroaches. Additionally, nymphs preferred a synthetic blend of 6 fecal VCAs over a solvent control or a previously identified VCA blend. To test whether gut bacteria contribute to the production of fecal aggregation agents, fecal aerobic bacteria were cultured, isolated, and identified. Inoculation of axenic cockroaches with individual bacterial taxa significantly rescued the aggregation response to the fecal extract, and inoculation with a mix of six bacterial isolates was more effective than with single isolates. The results indicate that the commensal gut microbiota contributes to production of VCAs that act as fecal aggregation agents and that cockroaches discriminate among the complex odors that emanate from a diverse microbial community. Our results highlight the pivotal role of gut bacteria in mediating insect–insect communication. Moreover, because the gut microbial community reflects the local environment, local plasticity in fecal aggregation pheromones enables colony-specific odors and fidelity to persistent aggregation sites. PMID:26644557

  18. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  19. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  20. Planktonic Aggregates of Staphylococcus aureus Protect against Common Antibiotics

    PubMed Central

    Haaber, Jakob; Cohn, Marianne Thorup; Frees, Dorte; Andersen, Thorbjørn Joest; Ingmer, Hanne

    2012-01-01

    Bacterial cells are mostly studied during planktonic growth although in their natural habitats they are often found in communities such as biofilms with dramatically different physiological properties. We have examined another type of community namely cellular aggregates observed in strains of the human pathogen Staphylococcus aureus. By laser-diffraction particle–size analysis (LDA) we show, for strains forming visible aggregates, that the aggregation starts already in the early exponential growth phase and proceeds until post-exponential phase where more than 90% of the population is part of the aggregate community. Similar to some types of biofilm, the structural component of S. aureus aggregates is the polysaccharide intercellular adhesin (PIA). Importantly, PIA production correlates with the level of aggregation whether altered through mutations or exposure to sub-inhibitory concentrations of selected antibiotics. While some properties of aggregates resemble those of biofilms including increased mutation frequency and survival during antibiotic treatment, aggregated cells displayed higher metabolic activity than planktonic cells or cells in biofilm. Thus, our data indicate that the properties of cells in aggregates differ in some aspects from those in biofilms. It is generally accepted that the biofilm life style protects pathogens against antibiotics and the hostile environment of the host. We speculate that in aggregate communities S. aureus increases its tolerance to hazardous environments and that the combination of a biofilm-like environment with mobility has substantial practical and clinical importance. PMID:22815921

  1. Marine Synechococcus Aggregation

    NASA Astrophysics Data System (ADS)

    Neuer, S.; Deng, W.; Cruz, B. N.; Monks, L.

    2016-02-01

    Cyanobacteria are considered to play an important role in the oceanic biological carbon pump, especially in oligotrophic regions. But as single cells are too small to sink, their carbon export has to be mediated by aggregate formation and possible consumption by zooplankton producing sinking fecal pellets. Here we report results on the aggregation of the ubiquitous marine pico-cyanobacterium Synechococcus as a model organism. We first investigated the mechanism behind such aggregation by studying the potential role of transparent exopolymeric particles (TEP) and the effects of nutrient (nitrogen or phosphorus) limitation on the TEP production and aggregate formation of these pico-cyanobacteria. We further studied the aggregation and subsequent settling in roller tanks and investigated the effects of the clays kaolinite and bentonite in a series of concentrations. Our results show that despite of the lowered growth rates, Synechococcus in nutrient limited cultures had larger cell-normalized TEP production, formed a greater volume of aggregates, and resulted in higher settling velocities compared to results from replete cultures. In addition, we found that despite their small size and lack of natural ballasting minerals, Synechococcus cells could still form aggregates and sink at measureable velocities in seawater. Clay minerals increased the number and reduced the size of aggregates, and their ballasting effects increased the sinking velocity and carbon export potential of aggregates. In comparison with the Synechococcus, we will also present results of the aggregation of the pico-cyanobacterium Prochlorococcus in roller tanks. These results contribute to our understanding in the physiology of marine Synechococcus as well as their role in the ecology and biogeochemistry in oligotrophic oceans.

  2. Challenges for simultaneous nitrification, denitrification, and phosphorus removal in microbial aggregates: mass transfer limitation and nitrous oxide production.

    PubMed

    Meyer, Rikke Louise; Zeng, Raymond Jianxiong; Giugliano, Valerio; Blackall, Linda Louise

    2005-05-01

    The microbial community composition and activity was investigated in aggregates from a lab-scale bioreactor, in which nitrification, denitrification and phosphorus removal occurred simultaneously. The biomass was highly enriched for polyphosphate accumulating organisms facilitating complete removal of phosphorus from the bulk liquid; however, some inorganic nitrogen still remained at the end of the reactor cycle. This was ascribed to incomplete coupling of nitrification and denitrification causing NO(3)(-) accumulation. After 2 h of aeration, denitrification was dependent on the activity of nitrifying bacteria facilitating the formation of anoxic zones in the aggregates; hence, denitrification could not occur without simultaneous nitrification towards the end of the reactor cycle. Nitrous oxide was identified as a product of denitrification, when based on stored PHA as carbon source. This observation is of critical importance to the outlook of applying PHA-driven denitrification in activated sludge processes.

  3. Management of Microbial Communities through Transient Disturbances Enhances the Functional Resilience of Nitrifying Gas-Biofilters to Future Disturbances.

    PubMed

    Cabrol, Léa; Poly, Franck; Malhautier, Luc; Pommier, Thomas; Lerondelle, Catherine; Verstraete, Willy; Lepeuple, Anne-Sophie; Fanlo, Jean-Louis; Le Roux, Xavier

    2016-01-05

    Microbial communities have a key role for the performance of engineered ecosystems such as waste gas biofilters. Maintaining constant performance despite fluctuating environmental conditions is of prime interest, but it is highly challenging because the mechanisms that drive the response of microbial communities to disturbances still have to be disentangled. Here we demonstrate that the bioprocess performance and stability can be improved and reinforced in the face of disturbances, through a rationally predefined strategy of microbial resource management (MRM). This strategy was experimentally validated in replicated pilot-scale nitrifying gas-biofilters, for the two steps of nitrification. The associated biological mechanisms were unraveled through analysis of functions, abundances and community compositions for the major actors of nitrification in these biofilters, that is, ammonia-oxidizing bacteria (AOB) and Nitrobacter-like nitrite-oxidizers (NOB). Our MRM strategy, based on the application of successive, transient perturbations of increasing intensity, enabled to steer the nitrifier community in a favorable way through the selection of more resistant AOB and NOB sharing functional gene sequences close to those of, respectively, Nitrosomonas eutropha and Nitrobacter hamburgensis that are well adapted to high N load. The induced community shifts resulted in significant enhancement of nitrification resilience capacity following the intense perturbation.

  4. Simultaneous removal of 2-chlorophenol, phenol, p-cresol and p-hydroxybenzaldehyde under nitrifying conditions: kinetic study.

    PubMed

    Silva, C D; Gómez, J; Beristain-Cardoso, R

    2011-06-01

    The kinetic behavior of a stable nitrifying consortium exposed to 2-chlorophenol (2-CP), phenol, p-cresol and p-hydroxybenzaldehyde (p-OHB) was evaluated in batch assays. Phenolic compounds were evaluated either individually or in mixture. In individual assays, 2-CP inhibited stronger the nitrification, diminishing the ammonium consumption efficiency (16%) and the nitrate production rate (at 91%). Nonetheless, the consumption efficiencies for all phenolics were of 100%. On the other hand, in mixture, the inhibitory effect of 2-CP diminished significantly, since ammonium consumption efficiency and nitrate production rate were improved. Consumption efficiencies for most of the phenolic compounds were high. Furthermore, the kinetic of 2-CP oxidation was 2.4-fold-faster than the individual assays. Finally, the experimental results showed the potential of nitrifying consortium for removing 2-CP, phenol, p-cresol and p-OHB. This is the first work showing the simultaneous removal of these pollutants and also this information might be useful for treating wastewaters of chemical complexity. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Thaumarchaeotes abundant in refinery nitrifying sludges express amoA but are not obligate autotrophic ammonia oxidizers

    PubMed Central

    Mußmann, Marc; Brito, Ivana; Pitcher, Angela; Sinninghe Damsté, Jaap S.; Hatzenpichler, Roland; Richter, Andreas; Nielsen, Jeppe L.; Nielsen, Per Halkjær; Müller, Anneliese; Daims, Holger; Wagner, Michael; Head, Ian M.

    2011-01-01

    Nitrification is a core process in the global nitrogen cycle that is essential for the functioning of many ecosystems. The discovery of autotrophic ammonia-oxidizing archaea (AOA) within the phylum Thaumarchaeota has changed our perception of the microbiology of nitrification, in particular since their numerical dominance over ammonia-oxidizing bacteria (AOB) in many environments has been revealed. These and other data have led to a widely held assumption that all amoA-encoding members of the Thaumarchaeota (AEA) are autotrophic nitrifiers. In this study, 52 municipal and industrial wastewater treatment plants were screened for the presence of AEA and AOB. Thaumarchaeota carrying amoA were detected in high abundance only in four industrial plants. In one plant, thaumarchaeotes closely related to soil group I.1b outnumbered AOB up to 10,000-fold, and their numbers, which can only be explained by active growth in this continuous culture system, were two to three orders of magnitude higher than could be sustained by autotrophic ammonia oxidation. Consistently, 14CO2 fixation could only be detected in AOB but not in AEA in actively nitrifying sludge from this plant via FISH combined with microautoradiography. Furthermore, in situ transcription of archaeal amoA, and very weak in situ labeling of crenarchaeol after addition of 13CO2, was independent of the addition of ammonium. These data demonstrate that some amoA-carrying group I.1b Thaumarchaeota are not obligate chemolithoautotrophs. PMID:21930919

  6. Linking nitrifying biofilm characteristics and nitrification performance in moving-bed biofilm reactors for polluted raw water pretreatment.

    PubMed

    Zhang, Shuangfu; Wang, Yayi; He, Weitao; Xing, Meiyan; Wu, Min; Yang, Jian; Gao, Naiyun; Sheng, Guangyao; Yin, Daqiang; Liu, Shanhu

    2013-10-01

    Biofilm physiology was characterized by four biofilm constituents, i.e., polysaccharides, proteins (PN), humic-like substances and phospholipids (PL), for the first time to explore the relationships between biofilm characteristics and nitrification performance in moving-bed biofilm reactors (MBBRs) designed for pretreatment of polluted raw surface water for potable supply. The biofilm compositions depended highly on the balance of microbial decay and nitrification processes. The increased ammonia loading greatly regulated the community structure, promoting the dominance of nitrifiers and their proportions in the nitrifying biofilm. Nitrification rate and activity correlated linearly with the fractions of volatile solids (VS), PN and PL, which were related to nitrification processes in the biofilm. The specific biofilm activity demonstrated an exponential-asymptotic relationship with ratios of PN/VS and PL/VS. Thus, analyzing biofilm characteristics can be valid for estimating nitrification performance in MBBRs, and may offer engineers with basis to optimize MBBR design and operation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Carrier effects on tertiary nitrifying moving bed biofilm reactor: An examination of performance, biofilm and biologically produced solids.

    PubMed

    Forrest, Daina; Delatolla, Robert; Kennedy, Kevin

    2016-01-01

    Increasingly stricter ammonia and nitrogen release regulations with respect to wastewater effluents are creating a need for tertiary treatment systems. The moving bed biofilm reactor (MBBR) is being considered as an upgrade option for an increasing number of wastewater treatment facilities due to its small footprint and ease of operation. Despite the MBBRs creation as a system to remove nitrogen, recent research on MBBR systems showing that the system's performance is directly related to carrier surface area and is irrespective of carrier shape and type has been performed exclusively on chemical oxygen demand (COD) removal systems. Furthermore, the influence of carrier type on the solids produced by MBBR systems has also been exclusively studied for COD removal systems. This work investigates the effects of three specific carrier types on ammonia removal rates, biofilm morphology, along with solids production and settleability of tertiary nitrifying MBBR systems. The study concludes that carrier type has no significant effect on tertiary nitrifying MBBR system performance under steady, moderate loading conditions. The research does however highlight the propensity of greater surface area to volume carriers to become clogged under high loading conditions and that the high surface area carriers investigated in this study required longer adjustment periods to changes in loading after becoming clogged.

  8. Removal of trace organic contaminants by nitrifying activated sludge and whole-cell and crude enzyme extract of Trametes versicolor.

    PubMed

    Yang, Shufan; Hai, Faisal I; Nghiem, Long D; Roddick, Felicity; Price, William E

    2013-01-01

    The resistance of certain anthropogenic trace organic contaminants (TrOCs) to conventional wastewater treatment and their potential adverse effects on human and ecological health raise significant concerns and have prompted research on their bioremediation by white-rot fungi. This study compared the removal efficiencies of four widespread TrOCs: carbamazepine (CBZ), sulfamethoxazole (SMX), bisphenol A (BPA) and diclofenac (DCF), by nitrifying activated sludge as well as whole-cell and extracellular enzyme (laccase) extract of the white-rot fungus Trametes versicolor. Fungal whole-cell culture removed only BPA and DCF but with high efficiencies (>90%) while the mixed nitrifying culture removed all compounds, although by levels of only 5-40%. Rapid initial sorption on fungal mycelium (44 ± 13% for DCF) was observed; however, biodegradation governed the overall removal. Performance comparison between fungal whole-cell and extracellular extract revealed that, unlike BPA, a catalytic pathway independent of extracellular laccase was responsible for DCF removal. Addition of mediator (1-hydroxybenzotriazole) to extracellular extract improved the removal of SMX which bears an electron donor group, but not that of the resistant compound CBZ.

  9. Assay for determination of alpha-glucosidase and peptidase activity and location in a nitrifying trickling filter.

    PubMed

    Mustafa, N; Sörensson, F

    2001-12-01

    Enzymatic alpha-glucosidase and peptidase activity in a nitrifying trickling filter (NTF) at the Rya wastewater treatment plant, Göteborg, Sweden, was investigated to evaluate whether these activities can be used as indicators of heterotrophic activity and polymer degradation. Samples of the biofilm were taken from the NTF and incubated in sterile filtered effluent water from the NTF with the addition of soluble starch, peptone, and ammonium chloride. In order to determine the distribution of enzyme activities, the alpha-glucosidase and peptidase activities were measured in the biofilm samples, in the filtered effluent water from the NTF and in the water phase in which the biofilm was incubated. Activities of both enzymes were found both in the effluent water from the NTF and in the biofilm. The enzyme activities were elevated in the samples when starch and peptone were present. In addition, there was a significant inhibition of ammonium oxidation in samples incubated with starch and peptone. Thus, the presence of starch, peptone and ammonium resulted in increased activity of heterotrophs, which lead to an inhibition of the nitrifiers, probably via competition for available oxygen.

  10. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  11. Characteristic differences between saliva-dependent aggregation and adhesion of streptococci.

    PubMed Central

    Rosan, B; Malamud, D; Appelbaum, B; Golub, E

    1982-01-01

    Comparison of saliva-mediated aggregation of Streptococcus sanguis, Streptococcus mitis, and Streptococcus mutans and adhesion of these organisms to saliva-coated hydroxyapatite showed that there was no relationship between these two activities. Adsorption of salivary aggregating activity to bacteria appears to have little effect on the ability of the residual saliva to support adherence; conversely, adsorption of salivary adherence factors to hydroxyapatite does not affect aggregation. Although heating saliva significantly reduces bacterial aggregation, it has little or no effect on adherence. A comparison of aggregation and adhesion with serial dilutions of saliva demonstrated that adhesion could still be detected at 100 to 500-fold-lower concentrations of salivary protein that bacterial aggregation. These findings support the concept that aggregation and adherence involve two distinct mechanisms of microbial clearance in the oral cavity. PMID:6274804

  12. Bacterial Communities: Interactions to Scale

    PubMed Central

    Stubbendieck, Reed M.; Vargas-Bautista, Carol; Straight, Paul D.

    2016-01-01

    In the environment, bacteria live in complex multispecies communities. These communities span in scale from small, multicellular aggregates to billions or trillions of cells within the gastrointestinal tract of animals. The dynamics of bacterial communities are determined by pairwise interactions that occur between different species in the community. Though interactions occur between a few cells at a time, the outcomes of these interchanges have ramifications that ripple through many orders of magnitude, and ultimately affect the macroscopic world including the health of host organisms. In this review we cover how bacterial competition influences the structures of bacterial communities. We also emphasize methods and insights garnered from culture-dependent pairwise interaction studies, metagenomic analyses, and modeling experiments. Finally, we argue that the integration of multiple approaches will be instrumental to future understanding of the underlying dynamics of bacterial communities. PMID:27551280

  13. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  14. Aggregates of a cationic porphyrin as supramolecular probes for biopolymers.

    PubMed

    Occhiuto, Ilaria Giuseppina; Samperi, Mario; Trapani, Mariachiara; De Luca, Giovanna; Romeo, Andrea; Pasternack, Robert F; Scolaro, Luigi Monsù

    2015-12-01

    The copper(II) derivative of the dicationic trans-bis(N-methylpyridinium-4-yl)diphenylporphyrin (t-CuPagg) forms large fractal aggregates in aqueous solution under moderate ionic strength conditions. A kinetic investigation of the aggregation process allows for a choice of experimental conditions to quickly obtain stable assemblies in solution. These positively charged aggregates are able to interact efficiently with negatively charged chiral species, (including bacterial spores) leading to induced circular dichroism signals in the Soret region of the porphyrin, now acting as a sensitive chiroptical probe.

  15. In situ nitrification rates and activity of present nitrifiers in the bottom water layer of two Baltic coastal zones affected by different riverine nutrient loads

    NASA Astrophysics Data System (ADS)

    Bartl, I.; Münster Happel, E.; Riemann, L.; Voss, M.

    2016-02-01

    Baltic coastal zones are among the most eutrophied in the world receiving high loads of nitrogen from riverine inputs. However, not only the loads but also the internal dynamics in coastal zones might have positive feedback on eutrophication through efficient remineralisation of organic material in the bottom water. Therefore, we studied nitrification, which is a vital remineralisation process, near the seafloor along with the community of nitrifying microorganisms. We hypothesize that a high nutrient and organic matter load leads to elevated ammonium concentrations in coastal waters and thus stimulates nitrification rates and alters the nitrifying community. Here we present results from 3 cruises combining nitrification rate measurements by 15N-incubations with sequence-based analyses of present and active nitrifiers in the bottom water of two sites in the Baltic Sea receiving different nutrient loads. The first results from the Bonus projects COCOA and BLUEPRINT indicate an increase of nitrification rates with depth as well as distance from the river mouth. In situ rates in the bottom water of the nutrient rich Vistula plume range from 53 to 197 nmol L-1 d-1 and from 10 to 646 nmol L-1 d-1 during winter and summer, respectively. In the nutrient poor Öre estuary rates increased significantly by 11 nmol L-1 d-1 from the river mouth to the outermost station. The relationship between nitrification rates, nitrifiers and trophic state of the coastal zone shall be discussed.

  16. Nitrifier-induced denitrification is an important source of soil nitrous oxide and can be inhibited by a nitrification inhibitor 3,4-dimethylpyrazole phosphate.

    PubMed

    Shi, Xiuzhen; Hu, Hang-Wei; Zhu-Barker, Xia; Hayden, Helen; Wang, Juntao; Suter, Helen; Chen, Deli; He, Ji-Zheng

    2017-07-28

    Soil ecosystem represents the largest contributor to global nitrous oxide (N2 O) production, which is regulated by a wide variety of microbial communities in multiple biological pathways. A mechanistic understanding of these N2 O production biological pathways in complex soil environment is essential for improving model performance and developing innovative mitigation strategies. Here, combined approaches of the (15) N-(18) O labelling technique, transcriptome analysis, and Illumina MiSeq sequencing were used to identify the relative contributions of four N2 O pathways including nitrification, nitrifier-induced denitrification (nitrifier denitrification and nitrification-coupled denitrification) and heterotrophic denitrification in six soils (alkaline vs. acid soils). In alkaline soils, nitrification and nitrifier-induced denitrification were the dominant pathways of N2 O production, and application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) significantly reduced the N2 O production from these pathways; this is probably due to the observed reduction in the expression of the amoA gene in ammonia-oxidizing bacteria (AOB) in the DMPP-amended treatments. In acid soils, however, heterotrophic denitrification was the main source for N2 O production, and was not impacted by the application of DMPP. Our results provide robust evidence that the nitrification inhibitor DMPP can inhibit the N2 O production from nitrifier-induced denitrification, a potential significant source of N2 O production in agricultural soils. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  17. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  18. Propagation of Tau aggregates.

    PubMed

    Goedert, Michel; Spillantini, Maria Grazia

    2017-05-30

    Since 2009, evidence has accumulated to suggest that Tau aggregates form first in a small number of brain cells, from where they propagate to other regions, resulting in neurodegeneration and disease. Propagation of Tau aggregates is often called prion-like, which refers to the capacity of an assembled protein to induce the same abnormal conformation in a protein of the same kind, initiating a self-amplifying cascade. In addition, prion-like encompasses the release of protein aggregates from brain cells and their uptake by neighbouring cells. In mice, the intracerebral injection of Tau inclusions induced the ordered assembly of monomeric Tau, followed by its spreading to distant brain regions. Short fibrils constituted the major species of seed-competent Tau. The existence of several human Tauopathies with distinct fibril morphologies has led to the suggestion that different molecular conformers (or strains) of aggregated Tau exist.

  19. Marine aggregate dynamics

    NASA Astrophysics Data System (ADS)

    The direction and scope of the Office of Naval Research's Marine Aggregate Dynamics Accelerated Research Initiative will be the topic of an open-house style meeting February 14, 7:30-10:00 P.M. in Ballroom D of the Hyatt Regency New Orleans at the Louisiana Superdome. This meeting is scheduled during the AGU/American Society of Limnology and Oceanography Ocean Sciences Meeting February 12-16 in New Orleans.The critical focus of the ARI is the measurement and modeling of the dynamics of the biological, physical, chemical and molecular processes that drive aggregation and produce aggregates. This new ARI will provide funding in Fiscal Years 1991-1995 to identify and quantify mechanisms that determine the distribution, abundance and size spectrum of aggregated particulate matter in the ocean.

  20. Aggregation and Averaging.

    ERIC Educational Resources Information Center

    Siegel, Irving H.

    The arithmetic processes of aggregation and averaging are basic to quantitative investigations of employment, unemployment, and related concepts. In explaining these concepts, this report stresses need for accuracy and consistency in measurements, and describes tools for analyzing alternative measures. (BH)

  1. Aggregation of retail stores

    NASA Astrophysics Data System (ADS)

    Jensen, Pablo; Boisson, Jean; Larralde, Hernán

    2005-06-01

    We propose a simple model to understand the economic factors that induce aggregation of some businesses over small geographical regions. The model incorporates price competition with neighboring stores, transportation costs and the satisfaction probability of finding the desired product. We show that aggregation is more likely for stores selling expensive products and/or stores carrying only a fraction of the business variety. We illustrate our model with empirical data collected in the city of Lyon.

  2. Bacterial Vaginosis

    MedlinePlus

    ... Listen Español Text Size Email Print Share Bacterial Vaginosis Page Content Bacterial vaginosis (BV) is the most common vaginal infection in ... in harmful bacteria. The actual organism responsible for vaginosis hasn’t been clearly identified. BV is uncommon ...

  3. Orthogonal cross-seeding: an approach to explore protein aggregates in living cells.

    PubMed

    Hinz, Justyna; Gierasch, Lila M; Ignatova, Zoya

    2008-04-08

    Protein aggregation is associated with the pathology of many diseases, especially neurodegenerative diseases. A variety of structurally polymorphic aggregates or preaggregates including amyloid fibrils is accessible to any aggregating protein. Preaggregates are now believed to be the toxic culprits in pathologies rather than mature aggregates. Although clearly valuable, understanding the mechanism of formation and the structural characteristics of these prefibrillar species is currently lacking. We report here a simple new approach to map the nature of the aggregate core of transient aggregated species directly in the cell. The method is conceptually based on the highly discriminating ability of aggregates to recruit new monomeric species with equivalent molecular structure. Different soluble segments comprising parts of an amyloidogenic protein were transiently pulse-expressed in a tightly controlled, time-dependent manner along with the parent aggregating full-length protein, and their recruitment into the insoluble aggregate was monitored immunochemically. We used this approach to determine the nature of the aggregate core of the metastable aggregate species formed during the course of aggregation of a chimera containing a long polyglutamine repeat tract in a bacterial host. Strikingly, we found that different segments of the full-length protein dominated the aggregate core at different times during the course of aggregation. In its simplicity, the approach is also potentially amenable to screen also for compounds that can reshape the aggregate core and induce the formation of alternative nonamyloidogenic species.

  4. Protein aggregation and prionopathies.

    PubMed

    Renner, M; Melki, R

    2014-06-01

    Prion protein and prion-like proteins share a number of characteristics. From the molecular point of view, they are constitutive proteins that aggregate following conformational changes into insoluble particles. These particles escape the cellular clearance machinery and amplify by recruiting the soluble for of their constituting proteins. The resulting protein aggregates are responsible for a number of neurodegenerative diseases such as Creutzfeldt-Jacob, Alzheimer, Parkinson and Huntington diseases. In addition, there are increasing evidences supporting the inter-cellular trafficking of these aggregates, meaning that they are "transmissible" between cells. There are also evidences that brain homogenates from individuals developing Alzheimer and Parkinson diseases propagate the disease in recipient model animals in a manner similar to brain extracts of patients developing Creutzfeldt-Jacob's disease. Thus, the propagation of protein aggregates from cell to cell may be a generic phenomenon that contributes to the evolution of neurodegenerative diseases, which has important consequences on human health issues. Moreover, although the distribution of protein aggregates is characteristic for each disease, new evidences indicate the possibility of overlaps and crosstalk between the different disorders. Despite the increasing evidences that support prion or prion-like propagation of protein aggregates, there are many unanswered questions regarding the mechanisms of toxicity and this is a field of intensive research nowadays. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  5. Uncultured bacterial diversity in a seawater recirculating aquaculture system revealed by 16S rRNA gene amplicon sequencing.

    PubMed

    Lee, Da-Eun; Lee, Jinhwan; Kim, Young-Mog; Myeong, Jeong-In; Kim, Kyoung-Ho

    2016-04-01

    Bacterial diversity in a seawater recirculating aquaculture system (RAS) was investigated using 16S rRNA amplicon sequencing to understand the roles of bacterial communities in the system. The RAS was operated at nine different combinations of temperature (15°C, 20°C, and 25°C) and salinity (20‰, 25‰, and 32.5‰). Samples were collected from five or six RAS tanks (biofilters) for each condition. Fifty samples were analyzed. Proteobacteria and Bacteroidetes were most common (sum of both phyla: 67.2% to 99.4%) and were inversely proportional to each other. Bacteria that were present at an average of ≥ 1% included Actinobacteria (2.9%) Planctomycetes (2.0%), Nitrospirae (1.5%), and Acidobacteria (1.0%); they were preferentially present in packed bed biofilters, mesh biofilters, and maturation biofilters. The three biofilters showed higher diversity than other RAS tanks (aerated biofilters, floating bed biofilters, and fish tanks) from phylum to operational taxonomic unit (OTU) level. Samples were clustered into several groups based on the bacterial communities. Major taxonomic groups related to family Rhodobacteraceae and Flavobacteriaceae were distributed widely in the samples. Several taxonomic groups like [Saprospiraceae], Cytophagaceae, Octadecabacter, and Marivita showed a cluster-oriented distribution. Phaeobacter and Sediminicola-related reads were detected frequently and abundantly at low temperature. Nitrifying bacteria were detected frequently and abundantly in the three biofilters. Phylogenetic analysis of the nitrifying bacteria showed several similar OTUs were observed widely through the biofilters. The diverse bacterial communities and the minor taxonomic groups, except for Proteobacteria and Bacteroidetes, seemed to play important roles and seemed necessary for nitrifying activity in the RAS, especially in packed bed biofilters, mesh biofilters, and maturation biofilters.

  6. Protein aggregation in bacteria: the thin boundary between functionality and toxicity.

    PubMed

    Bednarska, Natalia G; Schymkowitz, Joost; Rousseau, Frederic; Van Eldere, Johan

    2013-09-01

    Misfolding and aggregation of proteins have a negative impact on all living organisms. In recent years, aggregation has been studied in detail due to its involvement in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's diseases, and type II diabetes--all associated with accumulation of amyloid fibrils. This research highlighted the central importance of protein homeostasis, or proteostasis for short, defined as the cellular state in which the proteome is both stable and functional. It implicates an equilibrium between synthesis, folding, trafficking, aggregation, disaggregation and degradation. In accordance with the eukaryotic systems, it has been documented that protein aggregation also reduces fitness of bacterial cells, but although our understanding of the cellular protein quality control systems is perhaps most detailed in bacteria, the use of bacterial proteostasis as a drug target remains little explored. Here we describe protein aggregation as a normal physiological process and its role in bacterial virulence and we shed light on how bacteria defend themselves against the toxic threat of aggregates. We review the impact of aggregates on bacterial viability and look at the ways that bacteria use to maintain a balance between aggregation and functionality. The proteostasis in bacteria can be interrupted via overexpression of proteins, certain antibiotics such as aminoglycosides, as well as antimicrobial peptides--all leading to loss of cell viability. Therefore intracellular protein aggregation and disruption of proteostatic balance in bacteria open up another strategy that should be explored towards the discovery of new antimicrobials.

  7. The cell aggregating propensity of probiotic actinobacterial isolates: isolation and characterization of the aggregation inducing peptide pheromone.

    PubMed

    Muthu Selvam, Ramu; Vinothini, Gopal; Palliyarai Thaiyammal, Sethuramalingam; Latha, Selvanathan; Chinnathambi, Arunachalam; Dhanasekaran, Dharumadurai; Padmanabhan, Parasuraman; Ali Alharbi, Sulaiman; Archunan, Govindaraju

    2016-01-01

    The auto-aggregating ability of a probiotic is a prerequisite for colonization and protection of the gastrointestinal tract, whereas co-aggregation provides a close interaction with pathogenic bacteria. Peptide pheromone mediated signaling has been studied in several systems. However, it has not yet been explored in prokaryotes, especially actinobacteria. Hence, in the present study, the diffusible aggregation promoting factor was purified from the culture supernatant of a potent actinobacterial probiont and characterized using 20 different actinobacterial cultures isolated from the gut region of chicken and goat. The results showed that the pheromone-like compound induces the aggregation propensity of treated isolates. The factor was found to be a heat stable, acidic pH resistant, low molecular weight peptide which enhances the biofilm forming ability of other actinobacterial isolates. The aggregation promoting factor represents a bacterial sex factor (pheromone) and its characterization confirms its usage in the probiotic formulation.

  8. A robust nitrifying community in a bioreactor at 50 °C opens up the path for thermophilic nitrogen removal.

    PubMed

    Courtens, Emilie Np; Spieck, Eva; Vilchez-Vargas, Ramiro; Bodé, Samuel; Boeckx, Pascal; Schouten, Stefan; Jauregui, Ruy; Pieper, Dietmar H; Vlaeminck, Siegfried E; Boon, Nico

    2016-09-01

    The increasing production of nitrogen-containing fertilizers is crucial to meet the global food demand, yet high losses of reactive nitrogen associated with the food production/consumption chain progressively deteriorate the natural environment. Currently, mesophilic nitrogen-removing microbes eliminate nitrogen from wastewaters. Although thermophilic nitrifiers have been separately enriched from natural environments, no bioreactors are described that couple these processes for the treatment of nitrogen in hot wastewaters. Samples from composting facilities were used as inoculum for the batch-wise enrichment of thermophilic nitrifiers (350 days). Subsequently, the enrichments were transferred to a bioreactor to obtain a stable, high-rate nitrifying process (560 days). The community contained up to 17% ammonia-oxidizing archaea (AOAs) closely related to 'Candidatus Nitrososphaera gargensis', and 25% nitrite-oxidizing bacteria (NOBs) related to Nitrospira calida. Incorporation of (13)C-derived bicarbonate into the respective characteristic membrane lipids during nitrification supported their activity as autotrophs. Specific activities up to 198±10 and 894±81 mg N g(-1) VSS per day for AOAs and NOBs were measured, where NOBs were 33% more sensitive to free ammonia. The NOBs were extremely sensitive to free nitrous acid, whereas the AOAs could only be inhibited by high nitrite concentrations, independent of the free nitrous acid concentration. The observed difference in product/substrate inhibition could facilitate the development of NOB inhibition strategies to achieve more cost-effective processes such as deammonification. This study describes the enrichment of autotrophic thermophilic nitrifiers from a nutrient-rich environment and the successful operation of a thermophilic nitrifying bioreactor for the first time, facilitating opportunities for thermophilic nitrogen removal biotechnology.

  9. Relative rates of nitric oxide and nitrous oxide production by nitrifiers, denitrifiers, and nitrate respirers. [Pseudomonas fluorescens; Serratia marcescens; Alcaligenes faecalis

    SciTech Connect

    Anderson, I.C.; Levine, J.S.

    1986-05-01

    The authors investigated the effect of the partial pressure of oxygen (pO/sub 2/) on the production of NO and N/sub 2/O by a wide variety of common soil nitrifying, denitrifying, and nitrate-respiring bacteria under laboratory conditions. The production of NO per cell was highest by autotrophic nitrifiers and was independent of pO/sub 2/ in the range tested (0.5 to 10%), whereas N/sub 2/O production was inversely proportional to pO/sub 2/. Nitrous oxide production was highest in the denitrifier Pseudomonas fluorescens, but only under anaerobic conditions. The molar ratio of NO/N/sub 2/O produced was usually greater than unity for nitrifiers and much less than unity for denitrifiers. Chemodenitrification was the major source of both the NO and N/sub 2/O produced by the nitrate respirer Serratia marcescens. Chemodenitrification was also a possible source of NO and N/sub 2/O produced by the nitrate respirer Serratia marcescens. Chemodenitrification was also a possible source of No and N/sub 2/O in nitrifier cultures but only when high concentrations of nitrite had accumulated or were added to the medium. Although most of the denitrifiers produced NO and N/sub 2/O only under anaerobic conditions, chemostat cultures of Alcaligenes faecalis continued to emit these gases even when the cultures were sprayed with air. Based upon these results, we predict that aerobic soils are primary sources of NO and that N/sub 2/O is produced only when there is sufficient soil moisture to provide the anaerobic microsites necessary for denitrification by either denitrifiers or nitrifiers.

  10. A robust nitrifying community in a bioreactor at 50 °C opens up the path for thermophilic nitrogen removal

    PubMed Central

    Courtens, Emilie NP; Spieck, Eva; Vilchez-Vargas, Ramiro; Bodé, Samuel; Boeckx, Pascal; Schouten, Stefan; Jauregui, Ruy; Pieper, Dietmar H; Vlaeminck, Siegfried E; Boon, Nico

    2016-01-01

    The increasing production of nitrogen-containing fertilizers is crucial to meet the global food demand, yet high losses of reactive nitrogen associated with the food production/consumption chain progressively deteriorate the natural environment. Currently, mesophilic nitrogen-removing microbes eliminate nitrogen from wastewaters. Although thermophilic nitrifiers have been separately enriched from natural environments, no bioreactors are described that couple these processes for the treatment of nitrogen in hot wastewaters. Samples from composting facilities were used as inoculum for the batch-wise enrichment of thermophilic nitrifiers (350 days). Subsequently, the enrichments were transferred to a bioreactor to obtain a stable, high-rate nitrifying process (560 days). The community contained up to 17% ammonia-oxidizing archaea (AOAs) closely related to ‘Candidatus Nitrososphaera gargensis', and 25% nitrite-oxidizing bacteria (NOBs) related to Nitrospira calida. Incorporation of 13C-derived bicarbonate into the respective characteristic membrane lipids during nitrification supported their activity as autotrophs. Specific activities up to 198±10 and 894±81 mg N g−1 VSS per day for AOAs and NOBs were measured, where NOBs were 33% more sensitive to free ammonia. The NOBs were extremely sensitive to free nitrous acid, whereas the AOAs could only be inhibited by high nitrite concentrations, independent of the free nitrous acid concentration. The observed difference in product/substrate inhibition could facilitate the development of NOB inhibition strategies to achieve more cost-effective processes such as deammonification. This study describes the enrichment of autotrophic thermophilic nitrifiers from a nutrient-rich environment and the successful operation of a thermophilic nitrifying bioreactor for the first time, facilitating opportunities for thermophilic nitrogen removal biotechnology. PMID:26894446

  11. Stimulative effect of the fungal biocontrol agent Fusarium oxysporum f.sp. Striga on abundance of nitrifying prokaryotes in a maize rhizosphere

    NASA Astrophysics Data System (ADS)

    Musyoki, Mary; Enowashu, Esther; Zimmermann, Judith; Muema, Esther; Wainright, Henry; Vanlauwe, Bernard; Cadisch, Georg; Rasche, Frank

    2014-05-01

    The integration of resistant crop varieties and Fusarium oxysporum f.sp. strigae (Foxy-2) strains as biological control agent (BCA) has shown to be an effective control of the weed Striga hermonthica which is parasitic to several cereals (e.g., maize) cultivated in Sub-Saharan Africa. Most studies have examined the efficacy of the BCA and its interactions with host crops, while overlooking the interplay among key microorganisms in the soil nitrogen (N) cycle. Hence, we postulated that both Foxy-2 and Striga pose threats to the indigenous plant root-associated microbial communities involved in N cycling through direct or indirect competition for nutrients and that the application of high quality organic residues would compensate these effects. The primary objective of this study was thus to assess the potential impact of Foxy-2 on indigenous nitrifying prokaryotes in maize rhizosphere cultivated on two distinct soils (sandy Ferric Alisol versus clayey Humic Nitisol) obtained from Machanga and Embu, respectively, in central Kenya. These soils were treated with or without Foxy-2 and Striga; and in combination with high quality (i.e. CN ratio; 13, lignins, 8.9 % and polyphenols, 1.7 %) organic residues (i.e., Tithonia diversifolia) as N source. Using quantitative polymerase chain reaction (qPCR), we followed at three pre-defined sampling dates (14, 28 and 42 days after planting) the responses of ammonia-oxidizing archaea (AOA) and bacteria (AOB), total bacteria and archaea in four treatments of a rhizobox experiment: (i) Foxy-2 plus Striga (F+S), (ii) Striga only (C+S), (iii) Foxy-2 plus Striga plus Tithonia diversifolia residues (F+S+T), and (iv) a non-treated control (C). Overall, the treatment effects on soil microbial populations were, in comparison to the clayey Embu soil, more pronounced in the sandy Machanga soil. Contrary to our expectations, we observed a distinct stimulative, but no resource competition effect of Foxy-2 on the abundance of AOA, as well as

  12. Effect of free ammonia concentration on monochloramine penetration within a nitrifying biofilm and its effect on activity, viability, and recovery.

    PubMed

    Pressman, Jonathan G; Lee, Woo Hyoung; Bishop, Paul L; Wahman, David G

    2012-03-01

    Chloramine has replaced free chorine for secondary disinfection at many water utilities because of disinfection by-product (DBP) regulations. Because chloramination provides a source of ammonia, there is a potential for nitrification when using chloramines. Nitrification in drinking water distribution systems is undesirable and may result in degradation of water quality and subsequent non-compliance with existing regulations. Thus, nitrification control is a major issue and likely to become increasingly important as chloramine use increases. In this study, monochloramine penetration and its effect on nitrifying biofilm activity, viability, and recovery was investigated and evaluated using microelectrodes and confocal laser scanning microscopy (CLSM). Monochloramine was applied to nitrifying biofilm for 24 h at two different chlorine to nitrogen (Cl(2):N) mass ratios (4:1 [4.4 mg Cl(2)/L] or 1:1 Cl(2):N [5.3 mg Cl(2)/L]), resulting in either a low (0.23 mg N/L) or high (4.2 mg N/L) free ammonia concentration. Subsequently, these biofilm samples were allowed to recover without monochloramine and receiving 4.2 mg N/L free ammonia. Under both monochloramine application conditions, monochloramine fully penetrated into the nitrifying biofilm within 24 h. Despite this complete monochloramine penetration, complete viability loss did not occur, and both biofilm samples subsequently recovered aerobic activity when fed only free ammonia. When monochloramine was applied with a low free ammonia concentration, dissolved oxygen (DO) fully penetrated, but with a high free ammonia concentration, complete cessation of aerobic activity (i.e., oxygen utilization) did not occur and subsequent analysis indicated that oxygen consumption still remained near the substratum. During the ammonia only recovery phase, different spatial recoveries were seen in each of the samples, based on oxygen utilization. It appears that the presence of higher free ammonia concentration allowed a

  13. Fibronectin Aggregation and Assembly

    PubMed Central

    Ohashi, Tomoo; Erickson, Harold P.

    2011-01-01

    The mechanism of fibronectin (FN) assembly and the self-association sites are still unclear and contradictory, although the N-terminal 70-kDa region (I1–9) is commonly accepted as one of the assembly sites. We previously found that I1–9 binds to superfibronectin, which is an artificial FN aggregate induced by anastellin. In the present study, we found that I1–9 bound to the aggregate formed by anastellin and a small FN fragment, III1–2. An engineered disulfide bond in III2, which stabilizes folding, inhibited aggregation, but a disulfide bond in III1 did not. A gelatin precipitation assay showed that I1–9 did not interact with anastellin, III1, III2, III1–2, or several III1–2 mutants including III1–2KADA. (In contrast to previous studies, we found that the III1–2KADA mutant was identical in conformation to wild-type III1–2.) Because I1–9 only bound to the aggregate and the unfolding of III2 played a role in aggregation, we generated a III2 domain that was destabilized by deletion of the G strand. This mutant bound I1–9 as shown by the gelatin precipitation assay and fluorescence resonance energy transfer analysis, and it inhibited FN matrix assembly when added to cell culture. Next, we introduced disulfide mutations into full-length FN. Three disulfide locks in III2, III3, and III11 were required to dramatically reduce anastellin-induced aggregation. When we tested the disulfide mutants in cell culture, only the disulfide bond in III2 reduced the FN matrix. These results suggest that the unfolding of III2 is one of the key factors for FN aggregation and assembly. PMID:21949131

  14. Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity

    NASA Astrophysics Data System (ADS)

    Rabbi, S. M. F.; Daniel, H.; Lockwood, P. V.; MacDonald, C.; Pereg, L.; Tighe, M.; Wilson, B. R.; Young, I. M.

    2016-09-01

    Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250–2000 μm) and micro-aggregates (53–250 μm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (μCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower μCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes.

  15. Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity

    PubMed Central

    Rabbi, S. M. F.; Daniel, H.; Lockwood, P. V.; Macdonald, C.; Pereg, L.; Tighe, M.; Wilson, B. R.; Young, I. M.

    2016-01-01

    Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250–2000 μm) and micro-aggregates (53–250 μm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (μCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower μCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes. PMID:27615807

  16. Observing Convective Aggregation

    NASA Astrophysics Data System (ADS)

    Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

    2017-06-01

    Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  17. Observing convective aggregation

    NASA Astrophysics Data System (ADS)

    Holloway, Christopher; Wing, Allison; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan; Turner, David; Zuidema, Paquita

    2017-04-01

    Convective self-aggregation was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad a distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  18. Screening of Debaryomyces hansenii Strains for Flavor Production under a Reduced Concentration of Nitrifying Preservatives Used in Meat Products.

    PubMed

    Flores, Mónica; Moncunill, Daniel; Montero, Rebeca; López-Díez, José Javier; Belloch, Carmela

    2017-05-17

    A total of 15 Debaryomyces hansenii strains from different food origins were genetically characterized and tested on a culture medium resembling the composition of fermented sausages but different concentrations of nitrifying preservatives. Genetic typing of the D. hansenii strains revealed two levels of discrimination: isolation source or strain specific. Different abilities to proliferate on culture media containing different concentrations of nitrate and nitrite, as sole nitrogen sources and in the presence of amino acids, were observed within D. hansenii strains. Overall metabolism of amino acids and generation of aroma compounds were related to the strain origin of isolation. The best producers of branched aldehydes and ethyl ester compounds were strains isolated from pork sausages. Strains from cheese and llama sausages were good producers of ester compounds and branched alcohols, while vegetable strains produced mainly acid compounds. Nitrate and nitrite reduction affected in different ways the production of volatiles by D. hansenii.

  19. Application of high rate nitrifying trickling filters to remove low concentrations of ammonia from reclaimed municipal wastewater.

    PubMed

    van den Akker, B; Holmes, M; Short, M D; Cromar, N J; Fallowfield, H J

    2010-01-01

    The interference of ammonia with the chlorination process is a problem for many reclaimed water treatment plant operators. This paper presents the findings from a series of pilot experiments that investigated the efficacy of high flow rate nitrifying trickling filters (NTFs) for the removal of low concentrations of ammonia (0.5-3.0 mg N L(-1)) from reclaimed wastewater. Results showed that nitrification was impeded by a combination of high organic carbon loads and aquatic snails, which consumed much of the active biomass. With adequate snail control, nitrification rates (0.3-1.1 g NH(4)-N m(-2) d(-1)) equivalent to that of traditional wastewater NTFs were achieved, despite operating under comparably low ammonia feed concentrations and high hydraulic flow rates.

  20. A shift in the archaeal nitrifier community in response to natural and anthropogenic disturbances in the northern Gulf of Mexico.

    PubMed

    Newell, Silvia E; Eveillard, Damien; McCarthy, Mark J; Gardner, Wayne S; Liu, Zhanfei; Ward, Bess B

    2014-02-01

    The Gulf of Mexico is affected by hurricanes and suffers seasonal hypoxia. The Deepwater Horizon oil spill impacted every trophic level in the coastal region. Despite their importance in bioremediation and biogeochemical cycles, it is difficult to predict the responses of microbial communities to physical and anthropogenic disturbances. Here, we quantify sediment ammonia-oxidizing archaeal (AOA) community diversity, resistance and resilience, and important geochemical factors after major hurricanes and the oil spill. Dominant AOA archetypes correlated with different geochemical factors, suggesting that different AOA are constrained by distinct parameters. Diversity was lowest after the hurricanes, showing weak resistance to physical disturbances. However, diversity was highest during the oil spill and coincided with a community shift, suggesting a new alternative stable state sustained for at least 1 year. The new AOA community was not significantly different from that at the spill site 1 year after the spill. This sustained shift in nitrifier community structure may be a result of oil exposure.

  1. Bacterial endophthalmitis.

    PubMed

    Durand, Marlene L

    2009-07-01

    Endophthalmitis refers to bacterial or fungal infection of the vitreous and/or aqueous humors of the eye. Bacterial endophthalmitis occurs most commonly after eye surgery or penetrating ocular trauma (exogenous endophthalmitis), but may also occur from hematogenous seeding during bacteremia (endogenous endophthalmitis). The presentation is usually acute, with eye pain and decreased vision. In exogenous endophthalmitis, infection is confined to the eye. There is no fever and minimal, if any, peripheral leukocytosis. Treatment includes direct injection of antibiotics into the vitreous, and vitrectomy in more severe cases. Systemic antibiotics are indicated in endogenous endophthalmitis; their role in exogenous endophthalmitis is controversial. Visual outcome depends on the virulence of the bacterial pathogen and the speed with which treatment is given. Acute bacterial endophthalmitis is a medical emergency, because delay in treatment may result in vision loss.

  2. [Bacterial vaginosis].

    PubMed

    Ostaszewska-Puchalska, Iwona; Zdrodowska-Stefanow, Bozena; Puciło, Katarzyna

    2004-09-01

    Bacterial vaginosis (BV) is one of the most common lower genital tract infections among women of childbearing age. This paper is a survey of literature data concerning epidemiology, pathogenesis, clinical and laboratory diagnostic criteria of this clinical syndrome.

  3. [Study on rapid start-up of a nitrifying process using aerobic granular sludge as seed sludge].

    PubMed

    Liu, Wen-Ru; Shen, Yao-Liang; Ding, Ling-Ling; Ding, Min

    2013-06-01

    Using synthetic ammonia-rich wastewater as influent, rapid start-up of the nitrification reactor was attained in a laboratory-scale column-type sequencing batch reactor (SBR) inoculated with aerobic granular sludge, by gradually increasing the influent NH4(+) -N concentration (100-1000 mg x L(-1)) and decreasing the hydraulic retention time (8-4 h) under mesophilic condition (28-30 degrees C). The influent loading rate of NH4(+) -N reached 3.9 kg x (m3 x d)(-1) and the average ammonia removal efficiency was above 95% within one month. Values of ammonia oxidizing rate (AOR) as high as 5.0 kg x (m3 x d)(-1) was obtained in the following operational stage with extremely high nitrogen loading rate. Nitrite accumulation obviously occurred during the start-up period. The nitrite accumulation rate reached 2-4.5 kg x (m3 x d)(-1) from day 25 to 70. In spite of the change in the feeding composition (COD/N ratio) and the frequent fluctuations of nitrogen loading rate, the granules maintained their structures, with the SVI of 30-40 mL x g(-1). The amount of granules with diameter larger than 0.21 mm was about 93% (mass fraction) of the total on day 36. The granular color changed from yellow to brownish-yellow, and some turned brown in this study. All these results suggested the critical role of aerobic granular sludge as seed sludge for the rapid start-up of nitrifying processes and the formation of nitrifying granules.

  4. Long-term starvation and subsequent recovery of nitrifiers in aerated submerged fixed-bed biofilm reactors.

    PubMed

    Elawwad, Abdelsalam; Sandner, Hendrik; Kappelmeyer, Uwe; Koeser, Heinz

    2013-01-01

    The effectiveness of three operational strategies for maintaining nitrifiers in bench-scale, aerated, submerged fixed-bed biofilm reactors (SFBBRs) during long-term starvation at 20 degrees C were evaluated. The operational strategies were characterized by the resulting oxidation-reduction potential (ORP) in the SFBBRs. The activity rates of the nitrifiers were measured and the activity decay was expressed by half-life times. It was found that anoxic and alternating anoxic/aerobic conditions were the best ways to preserve ammonia-oxidizing bacteria (AOB) during long starvation periods and resulted in half-life times of up to 34 and 28 days, respectively. Extended anaerobic conditions caused the half-life for AOB to decrease to 21 days. In comparison, the activity decay of nitrite-oxidizing bacteria (NOB) tended to be slightly faster. The activity of AOB biofilms that were kept for 97 days under anoxic conditions could be completely recovered in less than one week, while over 4 weeks was needed for AOB kept under anaerobic conditions. NOB were more sensitive to starvation and required longer recovery periods than AOB. For complete recovery, NOB needed approximately 7 weeks, regardless of the starvation conditions applied. Using the fluorescence in situ hybridization (FISH) technique, Nitrospira was detected as the dominant NOB genus. Among the AOB, the terminal restriction fragment length polymorphism (TRFLP) technique showed that during starvation and recovery periods, the relative frequency of species shifted to Nitrosomonas europaea/eutropha, regardless of the starvation condition. The consequences of these findings for the operation of SFBBRs under low-load and starvation conditions are discussed.

  5. Influence of silver nanoparticles and liberated silver ions on nitrifying sludge: ammonia oxidation inhibitory kinetics and mechanism.

    PubMed

    Giao, Nguyen Thanh; Limpiyakorn, Tawan; Kunapongkiti, Pattaraporn; Thuptimdang, Pumis; Siripattanakul-Ratpukdi, Sumana

    2017-04-01

    Silver nanoparticles (AgNPs) are widely used in commercial products because of their excellent antimicrobial activity. Entrance of AgNPs and its released Ag ions (Ag(+)) into wastewater treatment plants could harm ammonia oxidation (AO) process resulting in environmental problems. This study investigated inhibitory kinetics and mechanism of AO from nitrifying sludge influenced by AgNPs and Ag(+). The findings demonstrated that AgNPs and Ag(+) adversely influenced on AO. Silver ions were more toxic to AO than AgNPs, which was indicated by the lower inhibitory constant (K i ) of 0.29 mg/L compared to that of AgNPs (K i of 73.5 mg/L). Over the experimental period of 60 h, AgNPs at 1, 10, and 100 mg/L released Ag(+) in the average concentrations of 0.059, 0.171, and 0.503 mg/L, respectively. Silver nanoparticles of 1-100 mg/L inhibited AO by 45-74%, whereas Ag(+) of 0.05-0.50 mg/L inhibited AO by 53-94%. This suggested that the AgNP toxicity mainly derived from the liberated Ag(+). Scanning electron microscopy results revealed that AgNPs attached on microbial cell surfaces, and both AgNPs and Ag(+) induced cell morphological change from rod shape to shorter rod shape. Transmission electron microscopy showed that AgNPs and Ag(+) diminished the thickness of the outer layer and reduced the density of internal parts of the exposed microbial cells, which could be the reasons for the morphology change. Live/dead results also confirmed that AgNPs and Ag(+) damaged membrane integrity of cells in the nitrifying sludge. This study suggested that the primary mechanism for toxicity of AgNPs was the liberation of Ag(+) and then both of silver species caused cell death.

  6. Purification and characterization of a low-temperature hydroxylamine oxidase from heterotrophic nitrifier Acinetobacter sp. Y16.

    PubMed

    Zhang, Shu Mei; Li, Wei Guang; Zhang, Duo Ying; Huang, Xiao Fei; Qin, Wen; Sha, Chang Qing

    2014-07-01

    To purify a low-temperature hydroxylamine oxidase (HAO) from a heterotrophic nitrifying bacterium Acinetobacter sp. Y16 and investigate the enzyme property. A HAO was purified by an anion-exchange and gel-filtration chromatography from strain Y16. The purity and molecular mass were determined by RP-HPLC and SDS-PAGE. The HAO activity was detected by monitoring the reduction of potassium ferricyanide using hydroxylamine as substrate and ferricyanide as electron acceptor. The partial amino acid sequence was determined by mass spectrometry. The low-temperature HAO with a molecular mass of 61 kDa was purified from strain Y16 by an anion-exchange and gel-filtration chromatography. The enzyme exhibited an ability to oxidize hydroxylamine in wide temperature range (4-40 °C) in vitro using hydroxylamine as substrate and ferricyanide as electron acceptor. It was stable in the temperature range of 4 to 15 °C and pH range of 6.0 to 8.5 with less than 30% change in its activity. The optimal temperature and pH were 15 °C and 7.5, respectively. Three peptides were determined by mass spectrometry which were shown to be not identical to other reported HAOs. This is the first study to purify a low-temperature HAO from a heterotrophic nitrifier Acinetobacter sp. It differs from other reported HAOs in molecular mass and enzyme properties. The findings of the present study have suggested that the strain Y16 passes through a hydroxylamine-oxidizing process catalyzed by a low-temperature HAO for ammonium removal. Copyright © 2014 The Editorial Board of Biomedical and Environmental Sciences. Published by China CDC. All rights reserved.

  7. Comparative study of microbial community structure in integrated vertical-flow constructed wetlands for treatment of domestic and nitrified wastewaters.

    PubMed

    Chang, Jun-Jun; Wu, Su-Qing; Liang, Kang; Wu, Zhenbin; Liang, Wei

    2015-03-01

    Microbial processes play a vital important role in the removal of contaminants in constructed wetland (CW). However, the microbial physiology and community structure can be influenced by environmental conditions. In this study, four pilot-scale integrated vertical-flow constructed wetlands (IVCWs) were employed to treat domestic and nitrified wastewaters. The microbial properties, along with their response to wastewater quality characteristics and seasonal variation, were determined. The results showed higher Shannon-Weiner diversity (H) and evenness (E) index of fatty acids (FAs), and relative abundances of signature FAs in down-flow cells and in the systems fed with domestic wastewater (DW). The relative abundances of fungi and gram-negative and aerobic bacteria were greater in up-flow cells. The dominant anaerobic bacteria found in most cells might be accounted for the prevailing anaerobic environment within the wetland beds, which could mean that the system fed with nitrified wastewater (NW) should perform better in nitrogen removal. The redundancy analysis (RDA) showed that pollutant concentrations, especially organic matter, influence the FA compositions greatly, and the most significant difference of microbial community structures was detected in down-flow cells fed with DW and up-flow ones with NW. The branched FAs, which could be used to represent anaerobic bacteria, were observed in down-flow cells treating DW and had a significant positive correlation with chemical oxygen demand (COD) concentration, probably suggesting the important role of anaerobic bacteria in organic matter degradation in the IVCWs. Seasonal variation, however, did not greatly influence the microbial community structure in the IVCWs.

  8. Real-time PCR assay for the simultaneous quantification of nitrifying and denitrifying bacteria in activated sludge.

    PubMed

    Geets, Joke; de Cooman, Michaël; Wittebolle, Lieven; Heylen, Kim; Vanparys, Bram; De Vos, Paul; Verstraete, Willy; Boon, Nico

    2007-05-01

    In order to improve wastewater treatment processes, a need exists for tools that rapidly give detailed insight into the community structure of activated sludge, supplementary to chemical and physical data. In this study, the advantages of microarrays and quantitative polymerase chin reaction (PCR) methods were combined into a real-time PCR assay that allows the simultaneous quantification of phylogenetic and functional genes involved in nitrification and denitrification processes. Simultaneous quantification was possible along a 5-log dynamic range and with high linear correlation (R (2) > 0.98). The specificity of the assay was confirmed by cloning and sequencing analyses of PCR amplicons obtained from activated sludge. The real-time assay was validated on mixed liquid samples of different treatment plants, which varied in nitrogen removal rate. The abundance of ammonia oxidizers was in the order of magnitude of 10(6) down to 10(4) ml(-1), whereas nitrite oxidizers were less abundant (10(3)-10(1) order of magnitude). The results were in correspondence with the nitrite oxidation rate in the sludge types. As for the nirS, nirK, and nosZ gene copy numbers, their abundance was generally in the order of magnitude of 10(8)-10(5). When sludge samples were subjected to lab-scale perturbations, a decrease in nitrification rate was reflected within 18 h in the copy numbers of nitrifier genes (decrease with 1 to 5 log units), whereas denitrification genes remained rather unaffected. These results demonstrate that the method is a fast and accurate tool for the analysis of the (de)nitrifying community structure and size in both natural and engineered environmental samples.

  9. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  10. Invasive dreissenid mussels and benthic algae in Lake Michigan: characterizing effects on sediment bacterial communities.

    PubMed

    Lee, Philip O; McLellan, Sandra L; Graham, Linda E; Young, Erica B

    2015-01-01

    Dreissenid mussels have invaded the Laurentian Great Lakes causing dramatic changes to benthic-pelagic interactions. Despite research on food web impacts, there is limited data on mussel effects on benthic bacterial communities. This study examined effects of dreissenid mussels and benthic algae on sediment bacterial community composition and diversity. Triplicate experimental sediment plus lake water microcosms were used and either mussels, benthic algae or both were added. Changes in water nutrient chemistry and sediment bacterial communities were monitored using 16S rRNA amplicon sequencing, over 21 days. When mussels were present, nitrate and soluble reactive P increased significantly as the dominant N and P forms. Bacterial diversity increased in all microcosms, although bacterial community composition was distinct between treatment. Higher nitrate in mussel microcosms was accompanied by increases in nitrifying taxa (Nitrospira, Nitrosomonas), which are important in oxidizing mussel-excreted ammonium. Microcosms with algal additions showed increases in bacterial taxa capable of degrading algal cellulose, and Pelagibacter (SAR11) disappeared from all but control microcosms. This study suggests that bacterial communities in lake sediments respond to mussels and algae. Functional analysis of bacterial communities provides insights into changes in microbially mediated benthic nutrient transformations associated with invasive dreissenid mussels and benthic algae in lake ecosystems. © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  11. Light-induced aggregation of microbial exopolymeric substances.

    PubMed

    Sun, Luni; Xu, Chen; Zhang, Saijin; Lin, Peng; Schwehr, Kathleen A; Quigg, Antonietta; Chiu, Meng-Hsuen; Chin, Wei-Chun; Santschi, Peter H

    2017-08-01

    Sunlight can inhibit or disrupt the aggregation process of marine colloids via cleavage of high molecular weight compounds into smaller, less stable fragments. In contrast, some biomolecules, such as proteins excreted from bacteria can form aggregates via cross-linking due to photo-oxidation. To examine whether light-induced aggregation can occur in the marine environment, we conducted irradiation experiments on a well-characterized protein-containing exopolymeric substance (EPS) from the marine bacterium Sagitulla stellata. Our results show that after 1 h sunlight irradiation, the turbidity level of soluble EPS was 60% higher than in the dark control. Flow cytometry also confirmed that more particles of larger sized were formed by sunlight. In addition, we determined a higher mass of aggregates collected on filter in the irradiated samples. This suggests light can induce aggregation of this bacterial EPS. Reactive oxygen species hydroxyl radical and peroxide played critical roles in the photo-oxidation process, and salts assisted the aggregation process. The observation that Sagitulla stellata EPS with relatively high protein content promoted aggregation, was in contrast to the case where no significant differences were found in the aggregation of a non-protein containing phytoplankton EPS between the dark and light conditions. This, together with the evidence that protein-to-carbohydrate ratio of aggregates formed under light condition is significantly higher than that formed under dark condition suggest that proteins are likely the important component for aggregate formation. Light-induced aggregation provides new insights into polymer assembly, marine snow formation, and the fate/transport of organic carbon and nitrogen in the ocean. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Attachment of Escherichia coli to Soil Aggregates as Affected by Aggregate Water Content and Presence of Manure Constituents

    NASA Astrophysics Data System (ADS)

    Guber, A.; Pachepsky, Y.; Shelton, D. R.; Yu, O.

    2006-12-01

    Many soils contain relatively large structural units that do not slack when soil is being wetted. Soil aggregates, obtained from dry soil samples by sieving, present a model media to study the interactions of intact soils with dissolved or suspended contaminants. Land-applied manures may contain various contaminants that cause water pollution and concomitant health problems. Some of these pollutants are bacteria, and Echerichia coli is widely used as an indicator of bacterial contamination. The objective of this work was to test the hypothesis that Echerichia coli attachment to soil aggregates is affected by aggregate size, aggregate water content, and presence of suspended manure colloids and dissolved organic compounds. Three aggregate fractions of 3.4-4.8 mm, 4.8-7.9 mm and 7.9-9.5 mm diameters were obtained by dry sieving of a loam soil. Air-dry and water-saturated aggregates were submerged in bacteria-water and bacteria-manure suspensions at four E. coli concentrations for 24 h. Amounts of attached E. coli were calculated from the difference between the amount applied and the amount remained in the suspension. Significant differences in E. coli attachment to air-dry and saturated aggregates were found. Both increase in water content and the presence of manure significantly decreased the Echerichia coli attachment to all aggregate fractions regardless of the aggregate size. Because E. coli transport in soil generally occurs through large pores between structural units when rainfall follows manure application, the decrease in bacteria attachment as a result of soil saturation and presence of suspended or dissolved manure components can enhance bacterial mobility and increase risk of ground water contamination.

  13. Aggregates, broccoli and cauliflower

    NASA Astrophysics Data System (ADS)

    Grey, Francois; Kjems, Jørgen K.

    1989-09-01

    Naturally grown structures with fractal characters like broccoli and cauliflower are discussed and compared with DLA-type aggregates. It is suggested that the branching density can be used to characterize the growth process and an experimental method to determine this parameter is proposed.

  14. Cold temperature decreases bacterial species richness in nitrogen-removing bioreactors treating inorganic mine waters.

    PubMed

    Karkman, A; Mattila, K; Tamminen, M; Virta, M

    2011-12-01

    Explosives used in mining, such as ammonium nitrate fuel oil (ANFO), can cause eutrophication of the surrounding environment by leakage of ammonium and nitrate from undetonated material that is not properly treated. Cold temperatures in mines affect nitrogen removal from water when such nutrients are treated with bioreactors in situ. In this study we identified bacteria in the bioreactors and studied the effect of temperature on the bacterial community. The bioreactors consisted of sequential nitrification and denitrification units running at either 5 or 10°C. One nitrification bioreactor running at 5°C was fed with salt spiked water. From the nitrification bioreactors, sequences from both ammonia- and nitrite-oxidizing bacteria were identified, but the species were distinct at different temperatures. The main nitrifiers in the lower temperature were closely related to the genera Nitrosospira and Candidatus Nitrotoga. 16S rRNA gene sequences closely related to halotolerant Nitrosomonas eutropha were found only from the salt spiked nitrification bioreactor. At 10°C the genera Nitrosomonas and Nitrospira were the abundant nitrifiers. The results showed that bacterial species richness estimates were low, <150 operational taxonomic units (OTUs), in all bioreactor clone libraries, when sequences were assigned to operational taxonomic units at an evolutionary distance of 0.03. The only exception was the nitrification bioreactor running at 10°C where species richness was higher, >300 OTUs. Species richness was lower in bioreactors running at 5°C compared to those operating at 10°C.

  15. Bacterial rheotaxis.

    PubMed

    Marcos; Fu, Henry C; Powers, Thomas R; Stocker, Roman

    2012-03-27

    The motility of organisms is often directed in response to environmental stimuli. Rheotaxis is the directed movement resulting from fluid velocity gradients, long studied in fish, aquatic invertebrates, and spermatozoa. Using carefully controlled microfluidic flows, we show that rheotaxis also occurs in bacteria. Excellent quantitative agreement between experiments with Bacillus subtilis and a mathematical model reveals that bacterial rheotaxis is a purely physical phenomenon, in contrast to fish rheotaxis but in the same way as sperm rheotaxis. This previously unrecognized bacterial taxis results from a subtle interplay between velocity gradients and the helical shape of flagella, which together generate a torque that alters a bacterium's swimming direction. Because this torque is independent of the presence of a nearby surface, bacterial rheotaxis is not limited to the immediate neighborhood of liquid-solid interfaces, but also takes place in the bulk fluid. We predict that rheotaxis occurs in a wide range of bacterial habitats, from the natural environment to the human body, and can interfere with chemotaxis, suggesting that the fitness benefit conferred by bacterial motility may be sharply reduced in some hydrodynamic conditions.

  16. Bacterial vaginosis.

    PubMed

    Weaver, C H; Mengel, M B

    1988-08-01

    Bacterial vaginosis (nonspecific vaginitis) is a polymicrobial, superficial vaginal infection caused by an increase in anaerobic organisms and a concomitant decrease in lactobacilli. Gardnerella vaginalis, once thought to be the sole etiologic agent, is probably one of several endogenous members of the vaginal flora that overgrow in women with bacterial vaginosis. Whether the growth of anaerobes or a primary decrease in lactobacilli is the initial pathogenic event remains unclear. Epidemiological studies have revealed that current or previous infections caused by Trichomonas organisms, increased sexual activity, and intrauterine device use are risk factors for this condition. Studies have indicated that bacterial vaginosis, previously thought to be a benign illness, is associated with some morbidity in pregnant women. Symptoms remain unreliable in the diagnosis of bacterial vaginosis. Diagnostic efficacy is best achieved by utilizing clinical signs. Assessment of cure is best accomplished by Gram stain, not clinical criteria. Metronidazole, 500 mg orally for seven days, remains the treatment of choice; however, a 2-g single dose of metronidazole represents a reasonable alternative if cost and compliance issues predominate in a clinical situation. Although a recent study supports the contention that treatment of the male sexual partner of women with bacterial vaginosis is effective, a general recommendation cannot be made with confidence on the issue of sexual partner treatment until other supporting work is done.

  17. Bacterial conjunctivitis

    PubMed Central

    2012-01-01

    Introduction Most cases of conjunctivitis in adults are probably due to viral infection, but children are more likely to develop bacterial conjunctivitis than they are viral forms. The main bacterial pathogens are Haemophilus influenzae and Streptococcus pneumoniae in adults and children, and Moraxella catarrhalis in children. Contact lens wearers may be more likely to develop gram-negative infections. Bacterial keratitis occurs in up to 30 per 100,000 contact lens wearers. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of empirical treatment in adults and children with suspected bacterial conjunctivitis? What are the effects of treatment in adults and children with bacteriologically confirmed bacterial conjunctivitis? What are the effects of treatment in adults and children with clinically confirmed gonococcal conjunctivitis? We searched: Medline, Embase, The Cochrane Library, and other important databases up to July 2011 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 44 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review we present information relating to the effectiveness and safety of the following interventions: ocular decongestants, oral antibiotics, parenteral antibiotics, saline, topical antibiotics, and warm compresses. PMID:22348418

  18. Bacterial conjunctivitis.

    PubMed

    Epling, John

    2012-02-20

    Most cases of conjunctivitis in adults are probably due to viral infection, but children are more likely to develop bacterial conjunctivitis than they are viral forms. The main bacterial pathogens are Haemophilus influenzae and Streptococcus pneumoniae in adults and children, and Moraxella catarrhalis in children. Contact lens wearers may be more likely to develop gram-negative infections. Bacterial keratitis occurs in up to 30 per 100,000 contact lens wearers. We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of empirical treatment in adults and children with suspected bacterial conjunctivitis? What are the effects of treatment in adults and children with bacteriologically confirmed bacterial conjunctivitis? What are the effects of treatment in adults and children with clinically confirmed gonococcal conjunctivitis? We searched: Medline, Embase, The Cochrane Library, and other important databases up to July 2011 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We found 44 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. In this systematic review we present information relating to the effectiveness and safety of the following interventions: ocular decongestants, oral antibiotics, parenteral antibiotics, saline, topical antibiotics, and warm compresses.

  19. Bacterial rheotaxis

    PubMed Central

    Marcos; Fu, Henry C.; Powers, Thomas R.; Stocker, Roman

    2012-01-01

    The motility of organisms is often directed in response to environmental stimuli. Rheotaxis is the directed movement resulting from fluid velocity gradients, long studied in fish, aquatic invertebrates, and spermatozoa. Using carefully controlled microfluidic flows, we show that rheotaxis also occurs in bacteria. Excellent quantitative agreement between experiments with Bacillus subtilis and a mathematical model reveals that bacterial rheotaxis is a purely physical phenomenon, in contrast to fish rheotaxis but in the same way as sperm rheotaxis. This previously unrecognized bacterial taxis results from a subtle interplay between velocity gradients and the helical shape of flagella, which together generate a torque that alters a bacterium's swimming direction. Because this torque is independent of the presence of a nearby surface, bacterial rheotaxis is not limited to the immediate neighborhood of liquid–solid interfaces, but also takes place in the bulk fluid. We predict that rheotaxis occurs in a wide range of bacterial habitats, from the natural environment to the human body, and can interfere with chemotaxis, suggesting that the fitness benefit conferred by bacterial motility may be sharply reduced in some hydrodynamic conditions. PMID:22411815

  20. Microbial properties of soil aggregates created by earthworms and other factors: spherical and prismatic soil aggregates from unreclaimed post-mining sites.

    PubMed

    Frouz, J; Krištůfek, V; Livečková, M; van Loo, D; Jacobs, P; Van Hoorebeke, L

    2011-01-01

    Soil aggregates between 2 and 5 mm from 35- and 45-year-old unreclaimed post-mining sites near Sokolov (Czech Republic) were divided into two groups: spherical and prismatic. X-ray tomography indicated that prismatic aggregates consisted of fragments of claystone bonded together by amorphous clay and roots while spherical aggregates consisted of a clay matrix and organic fragments of various sizes. Prismatic aggregates were presumed to be formed by plant roots and physical processes during weathering of Tertiary mudstone, while earthworms were presumed to contribute to the formation of spherical aggregates. The effects of drying and rewetting and glucose addition on microbial respiration, microbial biomass, and counts of bacteria in these aggregates were determined. Spherical aggregates contained a greater percentage of C and N and a higher C-to-N ratio than prismatic ones. The C content of the particulate organic matter was also higher in the spherical than in the prismatic aggregates. Although spherical aggregates had a higher microbial respiration and biomass, the growth of microbial biomass in spherical aggregates was negatively correlated with initial microbial biomass, indicating competition between bacteria. Specific respiration was negatively correlated with microbial biomass. Direct counts of bacteria were higher in spherical than in prismatic aggregates. Bacterial numbers were more stable in the center than in the surface layers of the aggregates. Transmission electron microscopy indicated that bacteria often occurred as individual cells in prismatic aggregates but as small clusters of cells in spherical aggregates. Ratios of colony forming units (cultivatable bacteria) to direct counts were higher in spherical than in prismatic aggregates. Spherical aggregates also contained faster growing bacteria.

  1. Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems

    PubMed Central

    Shaw, Jennifer L. A.; Weyrich, Laura S.; Sawade, Emma; Drikas, Mary; Cooper, Alan J.

    2015-01-01

    Drinking water assessments use a variety of microbial, physical, and chemical indicators to evaluate water treatment efficiency and product water quality. However, these indicators do not allow the complex biological communities, which can adversely impact the performance of drinking water distribution systems (DWDSs), to be characterized. Entire bacterial communities can be studied quickly and inexpensively using targeted metagenomic amplicon sequencing. Here, amplicon sequencing of the 16S rRNA gene region was performed alongside traditional water quality measures to assess the health, quality, and efficiency of two distinct, full-scale DWDSs: (i) a linear DWDS supplied with unfiltered water subjected to basic disinfection before distribution and (ii) a complex, branching DWDS treated by a four-stage water treatment plant (WTP) prior to disinfection and distribution. In both DWDSs bacterial communities differed significantly after disinfection, demonstrating the effectiveness of both treatment regimes. However, bacterial repopulation occurred further along in the DWDSs, and some end-user samples were more similar to the source water than to the postdisinfection water. Three sample locations appeared to be nitrified, displaying elevated nitrate levels and decreased ammonia levels, and nitrifying bacterial species, such as Nitrospira, were detected. Burkholderiales were abundant in samples containing large amounts of monochloramine, indicating resistance to disinfection. Genera known to contain pathogenic and fecal-associated species were also identified in several locations. From this study, we conclude that metagenomic amplicon sequencing is an informative method to support current compliance-based methods and can be used to reveal bacterial community interactions with the chemical and physical properties of DWDSs. PMID:26162884

  2. Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems.

    PubMed

    Shaw, Jennifer L A; Monis, Paul; Weyrich, Laura S; Sawade, Emma; Drikas, Mary; Cooper, Alan J

    2015-09-01

    Drinking water assessments use a variety of microbial, physical, and chemical indicators to evaluate water treatment efficiency and product water quality. However, these indicators do not allow the complex biological communities, which can adversely impact the performance of drinking water distribution systems (DWDSs), to be characterized. Entire bacterial communities can be studied quickly and inexpensively using targeted metagenomic amplicon sequencing. Here, amplicon sequencing of the 16S rRNA gene region was performed alongside traditional water quality measures to assess the health, quality, and efficiency of two distinct, full-scale DWDSs: (i) a linear DWDS supplied with unfiltered water subjected to basic disinfection before distribution and (ii) a complex, branching DWDS treated by a four-stage water treatment plant (WTP) prior to disinfection and distribution. In both DWDSs bacterial communities differed significantly after disinfection, demonstrating the effectiveness of both treatment regimes. However, bacterial repopulation occurred further along in the DWDSs, and some end-user samples were more similar to the source water than to the postdisinfection water. Three sample locations appeared to be nitrified, displaying elevated nitrate levels and decreased ammonia levels, and nitrifying bacterial species, such as Nitrospira, were detected. Burkholderiales were abundant in samples containing large amounts of monochloramine, indicating resistance to disinfection. Genera known to contain pathogenic and fecal-associated species were also identified in several locations. From this study, we conclude that metagenomic amplicon sequencing is an informative method to support current compliance-based methods and can be used to reveal bacterial community interactions with the chemical and physical properties of DWDSs.

  3. Effect of carbon source on acclimatization of nitrifying bacteria to achieve high-rate partial nitrification of wastewater with high ammonium concentration

    NASA Astrophysics Data System (ADS)

    Mousavi, Seyyed Alireza; Ibrahim, Shaliza; Aroua, Mohamed Kheireddine

    2017-03-01

    Experiments in two laboratory-scale sequential batch reactors were carried out to investigate the effect of heterotrophic bacteria on nitrifying bacteria using external carbon sources. Partial nitrification of ammonium-rich wastewater during short-term acclimatization enriched the activity of ammonia-oxidizing bacteria in both reactors. Heterotrophic bacteria exhibited a minor effect on nitrifying bacteria, and complete removal of ammonium occurred at a rate of 41 mg L-1 h-1 in both reactors. The main strategy of this research was to carry out partial nitrification using high-activity ammonia-oxidizing bacteria with a high concentration of free ammonia (70 mg L-1). The NO2 -/(NO3 - + NO2 -) ratio was greater than 0.9 in both reactors most of the time.

  4. Effect of carbon source on acclimatization of nitrifying bacteria to achieve high-rate partial nitrification of wastewater with high ammonium concentration

    NASA Astrophysics Data System (ADS)

    Mousavi, Seyyed Alireza; Ibrahim, Shaliza; Aroua, Mohamed Kheireddine

    2014-08-01

    Experiments in two laboratory-scale sequential batch reactors were carried out to investigate the effect of heterotrophic bacteria on nitrifying bacteria using external carbon sources. Partial nitrification of ammonium-rich wastewater during short-term acclimatization enriched the activity of ammonia-oxidizing bacteria in both reactors. Heterotrophic bacteria exhibited a minor effect on nitrifying bacteria, and complete removal of ammonium occurred at a rate of 41 mg L-1 h-1 in both reactors. The main strategy of this research was to carry out partial nitrification using high-activity ammonia-oxidizing bacteria with a high concentration of free ammonia (70 mg L-1). The NO2 -/(NO3 - + NO2 -) ratio was greater than 0.9 in both reactors most of the time.

  5. Ammonia oxidizing archaea are the predominant nitrifiers in disturbed and undisturbed southern US pine forests

    NASA Astrophysics Data System (ADS)

    Mushinski, R. M.; Boutton, T. W.; Gentry, T. J.; Dorosky, R. J.

    2016-12-01

    The rate-limiting step in nitrification, ammonia oxidation, is performed by both ammonia oxidizing bacteria (AOB) and archaea (AOA); however, reports on the relative contribution of each of these groups to forest soil nitrification has varied. We coupled qPCR and next generation sequencing of the amoA gene to a whole-soil assay that stimulates nitrification and allows for the discrimination of AOA- from AOB-activity using 1-octyne, which inhibits the activity of the bacterial ammonia monooxygenase. Soils, to a depth of 1 meter, were collected from replicated (n = 3) loblolly pine (Pinus taeda L.) stands subjected to three different intensities of timber harvest (i.e., unharvested old growth stands, bole-only harvest stands, and whole-tree harvest + forest floor removal stands). The abundance of both bacterial and archaeal amoA were influenced by harvest method and soil depth; furthermore, archaeal amoA was 13x more abundant than bacterial amoA, across all soil depths. Sequencing and subsequent annotation of the ammonia oxidizing community revealed that the AOA were dominated by Crenarchaeota and AOB were dominated by Nitrosospira. Surface mineral soils (0-10 cm) amended with 1-octyne revealed that approximately 67-86% of total nitrification can be attributable to AOA activity. The highest rates of nitrification (total and 1-octyne resistant) occurred in the soils taken from the unharvested reference stands which were significantly greater than harvested stands. We can conclude that in this pine forest system, AOA dominates AOB in regards to amoA copy number and ammonia oxidizing activity. Not only is this study one of the first to investigate the ammonia-oxidizing population in southern pine forests, but also illustrates that timber harvest can lead to long-term alterations in nitrogen cycle processes.

  6. Reversible Aggregation of Albumin

    NASA Astrophysics Data System (ADS)

    Colby, Ralph H.; Oates, Katherine M. N.; Krause, Wendy E.; Jones, Ronald L.

    2004-03-01

    We explore the interactions in synovial fluid involving the polyelectrolyte sodium hyaluronate (NaHA) and plasma proteins in their native state (albumin and globulins). Rheological measurements on synovial fluid show it to be highly viscoelastic and also rheopectic (stress increases with time in steady shear). Equilibrium dialysis confirms the findings of Ogston and Dubin that there is no association between NaHA and albumin at physiological pH and salt. What we find instead is a reversible aggregation of albumin, with an association energy of order 3kT and commensurate association lifetime of order microseconds. Certain anti-inflammatory drugs are shown to prevent this reversible aggregation. The implications of these findings for synovial fluid and blood rheology are discussed.

  7. Tracking protein aggregate interactions

    PubMed Central

    Bartz, Jason C; Nilsson, K Peter R

    2011-01-01

    Amyloid fibrils share a structural motif consisting of highly ordered β-sheets aligned perpendicular to the fibril axis.1, 2 At each fibril end, β-sheets provide a template for recruiting and converting monomers.3 Different amyloid fibrils often co-occur in the same individual, yet whether a protein aggregate aids or inhibits the assembly of a heterologous protein is unclear. In prion disease, diverse prion aggregate structures, known as strains, are thought to be the basis of disparate disease phenotypes in the same species expressing identical prion protein sequences.4–7 Here we explore the interactions reported to occur when two distinct prion strains occur together in the central nervous system. PMID:21597336

  8. Characterizing the Effect of Microhabitat on Bacterial Diversity in Sediments Along Topographic Gradients

    NASA Astrophysics Data System (ADS)

    Caspar, L.; Bushaw-Newton, K.

    2005-05-01

    Ongoing riparian restoration including the conversion of agricultural fields back to forested areas is being conducted within the Monocacy Wildlife Management area providing the opportunity to analyze bacterial microhabitat characteristics of sediments under varying degrees of disturbance. The objective of this study is to develop greater understanding of the role of physical and chemical microhabitat differences on bacterial presence within sediments in different habitat types (i.e., upland, riparian, and in-stream) and under different degrees of disturbance. Physical and chemical microhabitat components determined were temperature, percent sediment organic matter, percent sediment moisture, concentrations of ammonia, pH, and total sediment carbon and nitrogen. Total bacterial populations of sediment were measured using 4',6-diamidino-2-phenylindole (DAPI). Polymerase chain reactions have been performed selecting for universal bacterial genes and specific nitrogen fixing, nitrifying, and denitrification genes. Bacterial diversity measurements using denaturing gradient gel electrophoresis are ongoing. Remaining chemical and physical components of microhabitat have been completed and are being analyzed. Results indicate moisture inhibits bacterial abundance while nutrient presence in sediment is associated with larger bacterial biomass. These parameters of microhabitat do not have differing effects along elevations.

  9. Bacterial Tracheitis

    MedlinePlus

    ... Nears (News) Vaccination 101: Make Sure Kids Are Up to Date Additional Content Medical News Bacterial Tracheitis By Rajeev ... News HealthDay Vaccination 101: Make Sure Kids Are Up to Date MONDAY, Aug. 28, 2017 (HealthDay News) -- As the ...

  10. Sequence determinants of protein aggregation: tools to increase protein solubility

    PubMed Central

    Ventura, Salvador

    2005-01-01

    Escherichia coli is one of the most widely used hosts for the production of recombinant proteins. However, very often the target protein accumulates into insoluble aggregates in a misfolded and biologically inactive form. Bacterial inclusion bodies are major bottlenecks in protein production and are hampering the development of top priority research areas such structural genomics. Inclusion body formation was formerly considered to occur via non-specific association of hydrophobic surfaces in folding intermediates. Increasing evidence, however, indicates that protein aggregation in bacteria resembles to the well-studied process of amyloid fibril formation. Both processes appear to rely on the formation of specific, sequence-dependent, intermolecular interactions driving the formation of structured protein aggregates. This similarity in the mechanisms of aggregation will probably allow applying anti-aggregational strategies already tested in the amyloid context to the less explored area of protein aggregation inside bacteria. Specifically, new sequence-based approaches appear as promising tools to tune protein aggregation in biotechnological processes. PMID:15847694

  11. Zooplankton Aggregations Near Sills

    DTIC Science & Technology

    2003-09-30

    frequency echo-sounder system. This data were supplemented with multi-net (BIONESS) trawls, bongo nets, and otter trawls (operated by D. Mackas and group...side. The general composition of the zooplankton aggregations can be deduced from the relative levels of the three echo-sounder frequencies; krill ...Nov. 20th, 2002. Krill layer is evident at 66 – 90 m, coincident with BIONESS trawl through the region. 3 Figure 2 shows a comparison between

  12. Molecular phylogeny of heterotrophic nitrifiers and aerobic denitrifiers and their potential role in ammonium removal.

    PubMed

    Srivastava, Meenakshi; Kaushik, Manish Singh; Singh, Anumeha; Singh, Deepti; Mishra, Arun Kumar

    2016-08-01

    To investigate the physiology and taxonomic composition of the key players of nitrification and denitrification processes in paddy fields, culture dependent and independent studies have been carried out. A total of 28 bacterial strains have been screened in which six were capable of reducing nitrate and nitrite as well as having significant ammonium removal potential. 16S rRNA-PCR-DGGE-based molecular typing of enriched batch culture was done with time duration to explore and identify dominant and stable soil denitrifiers. Notably, three isolates namely PDN3, PDN19, PDN14 were found to be efficiently involved in the removal of 70.32, 71.46, and 81.50% of NH4 (+) and showed closest similarity (>98%) with Bacillus cereus, Bacillus subtilis, and Pseudomonas aeruginosa strains, respectively. The bacterial strain PDN14 showed maximum growth with highest ammonium removal rate (2.78 gN/(m(3) ·h) has also been characterized based on nosZ gene which showed similarity to uncultured γ- Proteobacteria, P. aeruginosa sp. B3. Median joining (MJ) network and rRNA secondary structure have been analyzed for their detailed taxonomic diversity and derived haplotype-based co-occurrence. Results demonstrated that such strains can serve as good candidate for in situ nitrogen transformation in paddy soils and improvingly characterized by physiological and detailed phylogenetic approaches.

  13. Proteins aggregation and human diseases

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2015-04-01

    Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

  14. Ecophysiology and Comparative Genomics of Nitrosomonas mobilis Ms1 Isolated from Autotrophic Nitrifying Granules of Wastewater Treatment Bioreactor.

    PubMed

    Thandar, Soe Myat; Ushiki, Norisuke; Fujitani, Hirotsugu; Sekiguchi, Yuji; Tsuneda, Satoshi

    2016-01-01

    Ammonia-oxidizing bacteria (AOB), which oxidize ammonia to nitrite in the first step of nitrification, play an important role in biological wastewater treatment systems. Nitrosomonas mobilis is an important and dominant AOB in various wastewater treatment systems. However, the detailed physiological and genomic properties of N. mobilis have not been thoroughly investigated because of limited success isolating pure cultures. This study investigated the key physiological characteristics of N. mobilis Ms1, which was previously isolated into pure culture from the nitrifying granules of wastewater treatment bioreactor. The pure culture of N. mobilis Ms1 was cultivated in liquid mineral medium with 30 mg-N L(-1) (2.14 mM) of ammonium at room temperature under dark conditions. The optimum growth of N. mobilis Ms1 occurred at 27°C and pH 8, with a maximum growth rate of 0.05-0.07 h(-1), which corresponded to a generation time of 10-14 h. The half saturation constant for ammonium uptake rate and the maximum ammonium uptake rate of N. mobilis Ms1 were 30.70 ± 0.51 μM NH4(+) and 0.01 ± 0.002 pmol NH4(+) cells(-1) h(-1), respectively. N. mobilis Ms1 had higher ammonia oxidation activity than N. europaea in this study. The oxygen uptake activity kinetics of N. mobilis Ms1 were Km(O2) = 21.74 ± 4.01 μM O2 and V max(O2) = 0.06 ± 0.02 pmol O2 cells(-1) h(-1). Ms1 grew well at ammonium and NaCl concentrations of up to 100 and 500 mM, respectively. The nitrite tolerance of N. mobilis Ms1 was extremely high (up to 300 mM) compared to AOB previously isolated from activated sludge and wastewater treatment plants. The average nucleotide identity between the genomes of N. mobilis Ms1 and other Nitrosomonas species indicated that N. mobilis Ms1 was distantly related to other Nitrosomonas species. The organization of the genes encoding protein inventory involved in ammonia oxidation and nitrifier denitrification processes were different from other Nitrosomonas species. The current

  15. Ecophysiology and Comparative Genomics of Nitrosomonas mobilis Ms1 Isolated from Autotrophic Nitrifying Granules of Wastewater Treatment Bioreactor

    PubMed Central

    Thandar, Soe Myat; Ushiki, Norisuke; Fujitani, Hirotsugu; Sekiguchi, Yuji; Tsuneda, Satoshi

    2016-01-01

    Ammonia-oxidizing bacteria (AOB), which oxidize ammonia to nitrite in the first step of nitrification, play an important role in biological wastewater treatment systems. Nitrosomonas mobilis is an important and dominant AOB in various wastewater treatment systems. However, the detailed physiological and genomic properties of N. mobilis have not been thoroughly investigated because of limited success isolating pure cultures. This study investigated the key physiological characteristics of N. mobilis Ms1, which was previously isolated into pure culture from the nitrifying granules of wastewater treatment bioreactor. The pure culture of N. mobilis Ms1 was cultivated in liquid mineral medium with 30 mg-N L-1 (2.14 mM) of ammonium at room temperature under dark conditions. The optimum growth of N. mobilis Ms1 occurred at 27°C and pH 8, with a maximum growth rate of 0.05–0.07 h-1, which corresponded to a generation time of 10–14 h. The half saturation constant for ammonium uptake rate and the maximum ammonium uptake rate of N. mobilis Ms1 were 30.70 ± 0.51 μM NH4+ and 0.01 ± 0.002 pmol NH4+ cells-1 h-1, respectively. N. mobilis Ms1 had higher ammonia oxidation activity than N. europaea in this study. The oxygen uptake activity kinetics of N. mobilis Ms1 were Km(O2) = 21.74 ± 4.01 μM O2 and V max(O2) = 0.06 ± 0.02 pmol O2 cells-1 h-1. Ms1 grew well at ammonium and NaCl concentrations of up to 100 and 500 mM, respectively. The nitrite tolerance of N. mobilis Ms1 was extremely high (up to 300 mM) compared to AOB previously isolated from activated sludge and wastewater treatment plants. The average nucleotide identity between the genomes of N. mobilis Ms1 and other Nitrosomonas species indicated that N. mobilis Ms1 was distantly related to other Nitrosomonas species. The organization of the genes encoding protein inventory involved in ammonia oxidation and nitrifier denitrification processes were different from other Nitrosomonas species. The current study

  16. Influence of wastewater composition on nutrient removal behaviors in the new anaerobic–anoxic/nitrifying/induced crystallization process

    PubMed Central

    Shi, Jing; Lu, Xiwu; Yu, Ran; Gu, Qian; Zhou, Yi

    2013-01-01

    In this study, the new anaerobic–anoxic/nitrifying/induced crystallization (A2N–IC) system was compared with anaerobic-anoxic/nitrifying (A2N) process to investigate nutrient removal performance under different influent COD and ammonia concentrations. Ammonia and COD removal rates were very stable in both processes, which were maintained at 84.9% and 86.6% when the influent ammonia varied from 30 mg L−1 to 45 mg L−1 and COD ranged from 250 mg L−1 to 300 mg L−1. The effluent phosphorus always maintained below 0.2 mg L−1 in A2N–IC, whereas in A2N the effluent phosphorus concentration was 0.4–1.7 mg L−1, demonstrating that A2N–IC is suitable to apply in a broader influent COD and ammonia concentration range. Under higher influent COD (300 mg L−1) or lower ammonia conditions (30 mg L−1), the main function of chemical induced crystallization was to coordinate better nutrient ratio for anoxic phosphorus uptake, whereas under high phosphorus concentration, it was to reduce phosphorus loading for biological system. Under the similar influent wastewater compositions, phosphorus release amounts were always lower in A2N–IC. To clarify the decrease procedure of phosphorus release in the A2N–IC, the equilibrium between chemical phosphorus removal and biological phosphorus removal in A2N–IC was analyzed by mass balance equations. During the long-term experiment, some undesirable phenomena were observed: the declining nitrification in post-aerobic tank and calcium phosphorus precipitation in the anaerobic tank. The reasons were analyzed; furthermore, the corresponding improvements were proposed. Nitrification effect could be enhanced in the post-aerobic tank, therefore ammonia removal rate could be increased; and biologically induced phosphorus precipitation could be inhibited by controlling pH at the anaerobic stage, so the phosphorus release and recovery could be improved. PMID:24596502

  17. Bacterially mediated mineralization of vaterite

    NASA Astrophysics Data System (ADS)

    Rodriguez-Navarro, Carlos; Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Alejandro; Gonzalez-Muñoz, Maria Teresa; Rodriguez-Gallego, Manuel

    2007-03-01

    Myxococcus xanthus, a common soil bacterium, plays an active role in the formation of spheroidal vaterite. Bacterial production of CO 2 and NH 3 and the transformation of the NH 3 to NH4+ and OH -, thus increasing solution pH and carbonate alkalinity, set the physicochemical conditions (high supersaturation) leading to vaterite precipitation in the microenvironment around cells, and directly onto the surface of bacterial cells. In the latter case, fossilization of bacteria occurs. Vaterite crystals formed by aggregation of oriented nanocrystals with c-axis normal to the bacterial cell-wall, or to the core of the spherulite when bacteria were not encapsulated. While preferred orientation of vaterite c-axis appears to be determined by electrostatic affinity (ionotropic effect) between vaterite crystal (0001) planes and the negatively charged functional groups of organic molecules on the bacterium cell-wall or on extracellular polymeric substances (EPS), analysis of the changes in the culture medium chemistry as well as high resolution transmission electron microscopy (HRTEM) observations point to polymorph selection by physicochemical (kinetic) factors (high supersaturation) and stabilization by organics, both connected with bacterial activity. The latter is in agreement with inorganic precipitation of vaterite induced by NH 3 and CO 2 addition in the protein-rich sterile culture medium. Our results as well as recent studies on vaterite precipitation in the presence of different types of bacteria suggest that bacterially mediated vaterite precipitation is not strain-specific, and could be more common than previously thought.

  18. Age-Dependent Protein Aggregation Initiates Amyloid-β Aggregation

    PubMed Central

    Groh, Nicole; Bühler, Anika; Huang, Chaolie; Li, Ka Wan; van Nierop, Pim; Smit, August B.; Fändrich, Marcus; Baumann, Frank; David, Della C.

    2017-01-01

    Aging is the most important risk factor for neurodegenerative diseases associated with pathological protein aggregation such as Alzheimer’s disease. Although aging is an important player, it remains unknown which molecular changes are relevant for disease initiation. Recently, it has become apparent that widespread protein aggregation is a common feature of aging. Indeed, several studies demonstrate that 100s of proteins become highly insoluble with age, in the absence of obvious disease processes. Yet it remains unclear how these misfolded proteins aggregating with age affect neurodegenerative diseases. Importantly, several of these aggregation-prone proteins are found as minor components in disease-associated hallmark aggregates such as amyloid-β plaques or neurofibrillary tangles. This co-localization raises the possibility that age-dependent protein aggregation directly contributes to pathological aggregation. Here, we show for the first time that highly insoluble proteins from aged Caenorhabditis elegans or aged mouse brains, but not from young individuals, can initiate amyloid-β aggregation in vitro. We tested the seeding potential at four different ages across the adult lifespan of C. elegans. Significantly, protein aggregates formed during the early stages of aging did not act as seeds for amyloid-β aggregation. Instead, we found that changes in protein aggregation occurring during middle-age initiated amyloid-β aggregation. Mass spectrometry analysis revealed several late-aggregating proteins that were previously identified as minor components of amyloid-β plaques and neurofibrillary tangles such as 14-3-3, Ubiquitin-like modifier-activating enzyme 1 and Lamin A/C, highlighting these as strong candidates for cross-seeding. Overall, we demonstrate that widespread protein misfolding and aggregation with age could be critical for the initiation of pathogenesis, and thus should be targeted by therapeutic strategies to alleviate neurodegenerative

  19. Interaction of multiple biomimetic antimicrobial polymers with model bacterial membranes.

    PubMed

    Baul, Upayan; Kuroda, Kenichi; Vemparala, Satyavani

    2014-08-28

    Using atomistic molecular dynamics simulations, interaction of multiple synthetic random copolymers based on methacrylates on prototypical bacterial membranes is investigated. The simulations show that the cationic polymers form a micellar aggregate in water phase and the aggregate, when interacting with the bacterial membrane, induces clustering of oppositely charged anionic lipid molecules to form clusters and enhances ordering of lipid chains. The model bacterial membrane, consequently, develops lateral inhomogeneity in membrane thickness profile compared to polymer-free system. The individual polymers in the aggregate are released into the bacterial membrane in a phased manner and the simulations suggest that the most probable location of the partitioned polymers is near the 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) clusters. The partitioned polymers preferentially adopt facially amphiphilic conformations at lipid-water interface, despite lacking intrinsic secondary structures such as α-helix or β-sheet found in naturally occurring antimicrobial peptides.

  20. Interaction of multiple biomimetic antimicrobial polymers with model bacterial membranes

    NASA Astrophysics Data System (ADS)

    Baul, Upayan; Kuroda, Kenichi; Vemparala, Satyavani

    2014-08-01

    Using atomistic molecular dynamics simulations, interaction of multiple synthetic random copolymers based on methacrylates on prototypical bacterial membranes is investigated. The simulations show that the cationic polymers form a micellar aggregate in water phase and the aggregate, when interacting with the bacterial membrane, induces clustering of oppositely charged anionic lipid molecules to form clusters and enhances ordering of lipid chains. The model bacterial membrane, consequently, develops lateral inhomogeneity in membrane thickness profile compared to polymer-free system. The individual polymers in the aggregate are released into the bacterial membrane in a phased manner and the simulations suggest that the most probable location of the partitioned polymers is near the 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) clusters. The partitioned polymers preferentially adopt facially amphiphilic conformations at lipid-water interface, despite lacking intrinsic secondary structures such as α-helix or β-sheet found in naturally occurring antimicrobial peptides.

  1. Interaction of multiple biomimetic antimicrobial polymers with model bacterial membranes

    SciTech Connect

    Baul, Upayan Vemparala, Satyavani; Kuroda, Kenichi

    2014-08-28

    Using atomistic molecular dynamics simulations, interaction of multiple synthetic random copolymers based on methacrylates on prototypical bacterial membranes is investigated. The simulations show that the cationic polymers form a micellar aggregate in water phase and the aggregate, when interacting with the bacterial membrane, induces clustering of oppositely charged anionic lipid molecules to form clusters and enhances ordering of lipid chains. The model bacterial membrane, consequently, develops lateral inhomogeneity in membrane thickness profile compared to polymer-free system. The individual polymers in the aggregate are released into the bacterial membrane in a phased manner and the simulations suggest that the most probable location of the partitioned polymers is near the 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) clusters. The partitioned polymers preferentially adopt facially amphiphilic conformations at lipid-water interface, despite lacking intrinsic secondary structures such as α-helix or β-sheet found in naturally occurring antimicrobial peptides.

  2. Human salivary aggregation in Streptococcus intermedius type g strains: relationship with IgA.

    PubMed

    Yamaguchi, Taihei

    2004-06-01

    Bacterial aggregation is an important step in elimination from the human body to protect against infection. Streptococcus intermedius K1K aggregates in human saliva. In this study, the salivary agglutinin was identified. The aggregation level was very strong in sonic-treated saliva and 1-microm filtrate. Preincubation of human saliva with anti-human alpha chain serum or anti-human whole saliva serum completely inhibited aggregation, but preincubation with anti-human micro chain serum or anti-Fc fragment of human IgG serum had no effect. Agglutinin of human saliva that could aggregate the strain K1K was purified using DEAE-Sepharose CL-6B, Phenyl-Sepharose CL-4B and Sephacryl S200HR gel filtration. Purified salivary agglutinin was characterized with electrophoresis and immunological techniques, indicating that purified material was IgA. Bacterial aggregation was dependent on the presence of calcium. Saliva filtrate specimens from eight healthy men and eight women showed different aggregation activities. Three men and one woman had little activity. These data show that the present bacterial aggregation was an immunoreaction between IgA in saliva and the bacteria dependent on the levels of calcium. In addition, the IgA in human saliva related with possible calcium-dependent antigen(s) on the surface of strain K1K.

  3. [Cell aggregation in cultures of Micrococcus luteus studied by dynamic light scattering].

    PubMed

    Voloshin, S A; Kaprel'iants, A S

    2005-01-01

    Cell aggregation was studied using the method of dynamic light scattering in the course of growth of Micrococcus luteus cultures in a liquid medium. The method detects particles ranging in size from 0.5 to 1000 microm in samples containing no more than 10(5) cells/ml. When grown in liquid media, M. luteus forms aggregates; during the lag phase, 80% of the cells are found in aggregates of 10 to 1000 microm, only minor amounts being represented by single cells. With the onset of exponential growth, the aggregates were decomposed, and single cells became prevalent in the culture liquid. This observation confirms that the aggregation of the cells during the lag phase is prerequisite to the initiation of bacterial growth. The method may be used in biotechnology for monitoring the state of bacterial cultures.

  4. Partial nitrifying granule stimulated by struvite carrier in treating pharmaceutical wastewater.

    PubMed

    Wang, Guowen; Wang, Dong; Xu, Xiaochen; Yang, Fenglin

    2013-10-01

    Aerobic granule was successfully cultivated in SBR (sequencing batch reactor) by struvite carrier (magnesium ammonium phosphate, MgNH4PO4), which can increase polysaccharides to 42.2 mg/gMLVSS (mixed liquor volatile suspended solid) versus only 28.4 mg/gMLVSS of the sludge without it. Meanwhile, it was found that struvite play a positive role in initial granulation and bacterial group distribution in treating pharmaceutical wastewater, involving effect of solid surface and special contents of struvite. The results of fluorescence in situ hybridization technique indicate that ammonia-oxidizing bacteria can dominate over nitrite-oxidizing bacteria in mature granules. COD removal efficiency of 90 % and NO2 (-)-N:(NO2 (-)-N + NO3 (-)-N) accumulation efficiency of 89 % were achieved in stable state. Emphasis is placed on that struvite addition can be applied as a new-type carrier to promote formation of partial nitrification granular sludge.

  5. Bacterial cryotomography

    NASA Astrophysics Data System (ADS)

    Jensen, Grant

    2009-03-01

    Electron cryotomography (ECT) is an emerging technique that allows thin samples such as small cells, viruses, or tissue sections to be imaged in 3-D in a near-native, ``frozen-hydrated'' state to molecular (˜4 nm) resolution. Thus ECT fills a critical gap between light microscopy and higher resolution structural techniques like X-ray crystallography and NMR. In a combination of technology development and biological application, during the past few years our lab has been studying bacterial ultrastructure through ECT of intact, plunge-frozen cells. We have now collected over a thousand tomograms of more than ten different species. This work has revealed the surprising complexity of the bacterial cytoskeleton as well as the architectures of several important ``supramolecular'' complexes including the chemoreceptor array, the flagellar motor, and the cell wall peptidoglycan. Example results highlighting both the potential and limitations of this technology will be shown.

  6. Non-Arrhenius protein aggregation.

    PubMed

    Wang, Wei; Roberts, Christopher J

    2013-07-01

    Protein aggregation presents one of the key challenges in the development of protein biotherapeutics. It affects not only product quality but also potentially impacts safety, as protein aggregates have been shown to be linked with cytotoxicity and patient immunogenicity. Therefore, investigations of protein aggregation remain a major focus in pharmaceutical companies and academic institutions. Due to the complexity of the aggregation process and temperature-dependent conformational stability, temperature-induced protein aggregation is often non-Arrhenius over even relatively small temperature windows relevant for product development, and this makes low-temperature extrapolation difficult based simply on accelerated stability studies at high temperatures. This review discusses the non-Arrhenius nature of the temperature dependence of protein aggregation, explores possible causes, and considers inherent hurdles for accurately extrapolating aggregation rates from conventional industrial approaches for selecting accelerated conditions and from conventional or more advanced methods of analyzing the resulting rate data.

  7. Ultrastructure of acetylcholine receptor aggregates parallels mechanisms of aggregation

    PubMed Central

    Kunkel, Dennis D; Lee, Lara K; Stollberg, Jes

    2001-01-01

    Background Acetylcholine receptors become aggregated at the developing neuromuscular synapse shortly after contact by a motorneuron in one of the earliest manifestations of synaptic development. While a major physiological signal for receptor aggregation (agrin) is known, the mechanism(s) by which muscle cells respond to this and other stimuli have yet to be worked out in detail. The question of mechanism is addressed in the present study via a quantitative examination of ultrastructural receptor arrangement within aggregates. Results In receptor rich cell membranes resulting from stimulation by agrin or laminin, or in control membrane showing spontaneous receptor aggregation, receptors were found to be closer to neighboring receptors than would be expected at random. This indicates that aggregation proceeds heterogeneously: nanoaggregates, too small for detection in the light microscope, underlie developing microaggregates of receptors in all three cases. In contrast, the structural arrangement of receptors within nanoaggregates was found to depend on the aggregation stimulus. In laminin induced nanoaggregates receptors were found to be arranged in an unstructured manner, in contrast to the hexagonal array of about 10 nm spacing found for agrin induced nanoaggregates. Spontaneous aggregates displayed an intermediate amount of order, and this was found to be due to two distinct population of nanoaggregates. Conclusions The observations support earlier studies indicating that mechanisms by which agrin and laminin-1 induced receptor aggregates form are distinct and, for the first time, relate mechanisms underlying spontaneous aggregate formation to aggregate structure. PMID:11749670

  8. The influence of erythrocyte aggregation on induced platelet aggregation.

    PubMed

    Ott, C; Lardi, E; Schulzki, T; Reinhart, W H

    2010-01-01

    Red blood cells (RBCs) affect platelet aggregation in flowing blood (primary hemostasis). We tested the hypothesis that RBC aggregation could influence platelet aggregation. RBC aggregation was altered in vitro by: (i) changing plasma aggregatory properties with 3.7 g% dextran 40 (D40), 3.0 g% dextran 70 (D70) or 1.55 g% dextran 500 (D500); (ii) changing RBC aggregatory properties by incubating RBCs in 50 mU/ml neuraminidase for 60 min (reduction of the surface sialic acid content, thus reducing electrostatic repulsion) and subsequent RBC resuspension in platelet rich plasma (PRP) containing 1 g% dextran 70. RBC aggregation was assessed with the sedimentation rate (ESR). Platelet aggregation was measured: (i) in flowing whole blood with a platelet function analyzer PFA-100(R), which simulates in vivo conditions with RBCs flowing in the center and platelets along the wall, where they adhere to collagen and aggregate; and (ii) in a Chrono-log 700 Aggregometer, which measures changes of impedance by platelet aggregation in whole blood or changes in light transmission in PRP. We found that RBC aggregation increased with increasing molecular weight of dextran (ESR: 4 +/- 3 mm/h, 34 +/- 14 mm/h and 89 +/- 23 mm/hfor D40, D70 and D500, respectively, p < 0.0001) and with neuraminidase-treated RBCs (76 +/- 27 mm/h vs 27 +/- 8 mm/h, respectively, p < 0.0001). Platelet aggregation measured in whole blood under flow conditions (PFA-100) and without flow (Chronolog Aggregometer) was not affected by RBC aggregation. Our data suggest that RBC aggregation does not affect platelet aggregation in vitro and plays no role in primary hemostasis.

  9. Novel nitrifiers and comammox in a full-scale hybrid biofilm and activated sludge reactor revealed by metagenomic approach.

    PubMed

    Chao, Yuanqing; Mao, Yanping; Yu, Ke; Zhang, Tong

    2016-09-01

    Biofilms are widely used in wastewater treatment for their particular enhancement of nitrogen removal and other significant advantages. In this study, the diversity and potential functions of nitrogen removal bacteria in suspended activated sludge (AS) and biofilm of a full-scale hybrid reactor were uncovered by metagenomes (∼34 Gb), coupled with PCR-based 454 reads (>33 K reads). The results indicated that the diversity and abundance of nitrifiers and denitrifiers in biofilm did not surpass that in AS, while more nitrification and denitrification genes were indeed found in biofilm than AS, suggesting that the increased nitrogen removal ability by applying biofilm might be attributed to the enhancement of removal efficiency, rather than the biomass accumulation of nitrogen removal bacteria. The gene annotation and phylogenetic analysis results revealed that AS and biofilm samples consisted of 6.0 % and 9.4 % of novel functional genes for nitrogen removal and 18 % and 30 % of new Nitrospira species for nitrite-oxidizing bacteria, respectively. Moreover, the identification of Nitrospira-like amoA genes provided metagenomic evidence for the presence of complete ammonia oxidizer (comammox) with the functional potential to perform the complete oxidation of ammonia to nitrate. These findings have significant implications in expanding our knowledge of the biological nitrogen transformations in wastewater treatment.

  10. Multi-species nitrifying biofilm model (MSNBM) including free ammonia and free nitrous acid inhibition and oxygen limitation.

    PubMed

    Park, Seongjun; Bae, Wookeun; Rittmann, Bruce E

    2010-04-15

    A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and oxygen limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients.

  11. Efficient model calibration method based on phase experiments for anaerobic-anoxic/nitrifying (A2N) two-sludge process.

    PubMed

    Dai, Hongliang; Chen, Wenliang; Dai, Zheqin; Li, Xiang; Lu, Xiwu

    2017-06-30

    A systematic calibration and validation procedure for the complex mechanistic modeling of anaerobic-anoxic/nitrifying (A2N) two-sludge system is needed. An efficient method based on phase experiments, sensitivity analysis, and genetic algorithm is proposed here for model calibration. Phase experiments (anaerobic phosphorus release, aerobic nitrification, and anoxic denitrifying phosphate accumulation) in an A2N sequencing batch reactor (SBR) were performed to reflect the process conditions accurately and improve the model calibration efficiency. The calibrated model was further validated using 30 batch experiments and 3-month dynamic continuous flow (CF) experiments for A2N-SBR and CF-A2N process, respectively. Several statistical criteria were conducted to evaluate the accuracy of model predications, including the average relative deviation (ARD), mean absolute error (MAE), root mean square error (RMSE), and Janus coefficient. Visual comparisons and statistical analyses indicated that the calibrated model could provide accurate predictions for the effluent chemical oxygen demand (COD), ammonia nitrogen (NH4(+)-N), total nitrogen (TN), and total phosphorus (TP), with only one iteration.

  12. Shifts in Nitrification Kinetics and Microbial Community during Bioaugmentation of Activated Sludge with Nitrifiers Enriched on Sludge Reject Water

    PubMed Central

    Yu, Lifang; Peng, Dangcong; Pan, Ruiling

    2012-01-01

    This study used two laboratory-scale sequencing batch reactors (SBRs) to evaluate the shifts in nitrification kinetics and microbial communities of an activated sludge sewage treatment system (main stream) during bioaugmentation with nitrifiers cultivated on real sludge reject water (side stream). Although bioaugmentation exerted a strong influence on the microbial community and the nitrification kinetics in the main stream, there was 58% of maximum ammonia uptake rate (AUR) and 80% of maximum nitrite uptake rate (NUR) loss of the seed source after bioaugmentation. In addition, nitrite accumulation occurred during bioaugmentation due to the unequal and asynchronous increase of the AUR (from 2.88 to 13.36 mg N/L·h) and NUR (from 0.76 to 4.34 mg N/L·h). FISH results showed that ammonia oxidizing bacteria (AOB) was inclined to be washed out with effluent in contrast to nitrite oxidizing bacteria (NOB), and Nitrosococcus mobilis lineage was the dominant AOB, while the dominant NOB in the main stream gradually transferred from Nitrospira to Nitrobacter. Nitrospina and Nitrococcus which existed in the seed source could not be detected in the main stream. It can be inferred that nitrite accumulation occurred due to the mismatch of NOB structure but washed out with effluent. PMID:23091354

  13. Ammonium removal at low temperature by a newly isolated heterotrophic nitrifying and aerobic denitrifying bacterium Pseudomonas fluorescens wsw-1001.

    PubMed

    Zhang, Shumei; Sha, Changqing; Jiang, Wei; Li, Weiguang; Zhang, Duoying; Li, Jing; Meng, Liqiang; Piao, Yongjian

    2015-01-01

    A heterotrophic nitrifier wsw-1001 was isolated from Songhua River and identified as Pseudomonas fluorescens. Ammonium removal by the strain at low temperature was investigated. The effect of initial ammonium concentration (from 5 to 1000 mg/L) and culture temperature (from 4°C to 30°C) on ammonium removal efficiency was studied. Biodegradation product, [Formula: see text], [Formula: see text], N2, N2O and intercellular N were monitored. The results indicated that the strain had potential for water and wastewater treatment. Ammonium could be removed by the strain at low temperature. Ammonium removal efficiency increased with temperature from 4°C to 20°C and decreased with ammonium concentration from 5 to 1000 mg/L. The strain exhibited a capability of heterotrophic nitrification and aerobic denitrification using [Formula: see text] as the sole nitrogen source at 8°C. [Formula: see text] and [Formula: see text] were reduced by the strain. Nitrogen balance analysis in the presence of 39.7 mg/L [Formula: see text] indicated that 71.2% [Formula: see text] was removed by converting to N2 (46.3%) and assimilating as biomass (42.5%). Substances such as [Formula: see text], [Formula: see text] and N2O were detected at very low concentrations. Ammonium mono-oxygenase, hydroxylamine oxidase, nitrite reductase and nitrate reductase activity were measured. The ammonium removal pathway of the strain was speculated to be [Formula: see text].

  14. Pre-nitrification by encapsulated nitrifiers--a possibility for self-sufficient energy operation of domestic WWTPs.

    PubMed

    Sievers, M; Vorlop, K D; Hahne, J; Schlieker, M; Schäfer, S

    2003-01-01

    The overall energy consumption of domestic wastewater treatment plants (WWTPs) increases with treatment efficiency. Approximately 30 to 45 kWh per people equivalent and year is mostly necessary for advanced nitrogen and phosphorus removal, while the aeration contains the main part of approximately 60%. A new process using encapsulated nitrifiers on gel lens beads is introduced to overcome the high energy consumption of aeration. A more selective nitrification process was found at a nitrification rate of between 50 and 60 mg nitrogen per hour and litre reaction volume corresponding to a hydraulic retention time (HRT) of about 30 to 60 minutes while the soluble Chemical Oxygen Demand (COD) removal could be less than 30% depending on operational conditions of the bio-reactor. The latter enables internal use of wastewater's COD for a post denitrification. For the new process the energy consumption as well as total volume of bio-reactor are much less (approximately 30 to 50% for both) than conventional processes due to the low sludge age for COD and nitrate removal and the avoidance of internal wastewater recycle. Therefore, self-sufficient energy operation of domestic WWTPs operating with advanced treatment efficiency could become possible, if energy recovery by anaerobic sludge digestion is included.

  15. Seasonal variations of nitrifying community in trickling filter-solids contact (TF/SC) activated sludge systems.

    PubMed

    Datta, Tania; Racz, LeeAnn; Kotay, Shireen Meher; Goel, Ramesh

    2011-02-01

    Two full-scale trickling filter/solids contact (TF/SC) basin plants, each successfully performing nitrification, were sampled throughout various seasons over a period of one year. Concentrations of ammonia, nitrate and nitrite were measured at various sampling locations along the treatment train. DNA was also extracted from mixed liquor in the solids contact basins. These DNA samples were subjected to terminal restriction fragment length polymorphism (TRFLP) in order to profile the ammonia oxidizing bacteria and nitrite oxidizing bacteria communities. In both plants, there was a prevalence of Nitrosomonas europaea among the ammonia oxidizing bacteria (AOBs). However, during the summer months, there was increased diversity of Nitrosomonas species. Likewise, Nitrospira spp. was the dominant nitrite oxidizing bacteria (NOBs) in both plants regardless of season. Yet there was an increased presence of Nitrobacter among the NOBs in the summer months. These results add an important understanding of the ecology and dynamics in nitrifying population in full-scale TF/SC wastewater treatment plants. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Making Graphene Resist Aggregation

    NASA Astrophysics Data System (ADS)

    Luo, Jiayan

    Graphene-based sheets have stimulated great interest in many scientific disciplines and shown promise for wide potential applications. Among various ways of creating single atomic layer carbon sheets, a promising route for bulk production is to first chemically exfoliate graphite powders to graphene oxide (GO) sheets, followed by reduction to form chemically modified graphene (CMG). Due to the strong van der Waals attraction between graphene sheets, CMG tends to aggregate. The restacking of sheets is largely uncontrollable and irreversible, thus it reduces their processability and compromises properties such as accessible surface area. Strategies based on colloidal chemistry have been applied to keep CMG dispersed in solvents by introducing electrostatic repulsion to overcome the van der Waals attraction or adding spacers to increase the inter-sheet spacing. In this dissertation, two very different ideas that can prevent CMG aggregation without extensively modifying the material or introducing foreign spacer materials are introduced. The van der Waals potential decreases with reduced overlapping area between sheets. For CMG, reducing the lateral dimension from micrometer to nanometer scale should greatly enhance their colloidal stability with additional advantages of increased charge density and decreased probability to interact. The enhanced colloidal stability of GO and CMG nanocolloids makes them especially promising for spectroscopy based bio-sensing applications. For potential applications in a compact bulk solid form, the sheets were converted into paper-ball like structure using capillary compression in evaporating aerosol droplets. The crumpled graphene balls are stabilized by locally folded pi-pi stacked ridges, and do not unfold or collapse during common processing steps. They can tightly pack without greatly reducing the surface area. This form of graphene leads to scalable performance in energy storage. For example, planer sheets tend to aggregate and

  17. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  18. Bacterial oxidation of dibromomethane and methyl bromide in natural waters and enrichment cultures

    USGS Publications Warehouse

    Goodwin, K.D.; Schaefer, J.K.; Oremland, R.S.

    1998-01-01

    Bacterial oxidation of 14CH2Br2 and 14CH3Br was measured in freshwater, estuarine, seawater, and hypersaline-alkaline samples. In general, bacteria from the various sites oxidized similar amounts of 14CH2Br2 and comparatively less 14CH3Br. Bacterial oxidation of 14CH3Br was rapid in freshwater samples compared to bacterial oxidation of 14CH3Br in more saline waters. Freshwater was also the only site in which methyl fluoride-sensitive bacteria (e.g., methanotrophs or nitrifiers) governed brominated methane oxidation. Half-life calculations indicated that bacterial oxidation of CH2Br2 was potentially significant in all of the waters tested. In contrast, only in freshwater was bacterial oxidation of CH3Br as fast as chemical removal. The values calculated for more saline sites suggested that bacterial oxidation of CH3Br was relatively slow compared to chemical and physical loss mechanisms. However, enrichment cultures demonstrated that bacteria in seawater can rapidly oxidize brominated methanes. Two distinct cultures of nonmethanotrophic methylotrophs were recovered; one of these cultures was able to utilize CH2Br2 as a sole carbon source, and the other was able to utilize CH3Br as a sole carbon source.

  19. An electrophoretic study of the thermal- and reductant-dependent aggregation of the 27 kDa component of ammonia monooxygenase from Nitrosomonas europaea.

    PubMed

    Hyman, M R; Arp, D J

    1993-07-01

    Standard protocols for sample preparation for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) typically involve the combined use of heat and a reductant to fully disrupt protein-protein interactions and allow for constant ratios of SDS-binding to individual polypeptides. However, 14C-labeled forms of the membrane-bound, active-site-containing 27 kDa polypeptide of ammonia monooxygenase from Nitrosomonas europaea undergo an aggregation reaction when cells or membranes are heated in the presence of SDS-PAGE sample buffer. The aggregate produced after heating at 100 degrees C is a soluble complex which fails to enter the stacking gel in discontinuous SDS-PAGE gels. The extent of the aggregation reaction is dependent on the temperature of sample preparation, and the reaction exhibits first-order kinetics at 65 degrees C and 100 degrees C (rates constants = 0.07 and 0.35 min-1, respectively). The rate of the aggregation reaction is further dependent on the concentration of reductant used in the sample buffer. However, the concentration of SDS does not significantly affect the rate of aggregation. The aggregated form of the 27 kDA polypeptide can be isolated by gel-permeation chromatography in the presence of SDS. The aggregated protein can also be returned to the monomeric state by incubation at high pH in the presence of SDS. The aggregation reaction also occurs with 14C2H2-labeled polypeptides in other species of autotrophic nitrifiers and a methanotrophic bacterium which expresses the particulate form of methane monooxygenase. We conclude that strongly hydrophobic amino acid sequences present in ammonia monooxygenase are responsible for the aggregation phenomenon.

  20. Population ecology of nitrifying archaea and bacteria in the Southern California Bight.

    PubMed

    Beman, J Michael; Sachdeva, Rohan; Fuhrman, Jed A

    2010-05-01

    Marine Crenarchaeota are among the most abundant microbial groups in the ocean, and although relatively little is currently known about their biogeochemical roles in marine ecosystems, recognition that Crenarchaeota posses ammonia monooxygenase (amoA) genes and may act as ammonia-oxidizing archaea (AOA) offers another means of probing the ecology of these microorganisms. Here we use a time series approach combining quantification of archaeal and bacterial ammonia oxidizers with bacterial community fingerprints and biogeochemistry, to explore the population and community ecology of nitrification. At multiple depths (150, 500 and 890 m) in the Southern California Bight sampled monthly from 2003 to 2006, AOA were enumerated via quantitative PCR of archaeal amoA and marine group 1 Crenarchaeota 16S rRNA genes. Based on amoA genes, AOA were highly variable in time - a consistent feature of marine Crenarchaeota- however, average values were similar at different depths and ranged from 2.20 to 2.76 x 10(4) amoA copies ml(-1). Archaeal amoA genes were correlated with Crenarchaeota 16S rRNA genes (r(2) = 0.79) and the slope of this relationship was 1.02, demonstrating that the majority of marine group 1 Crenarchaeota present over the dates and depths sampled possessed amoA. Two AOA clades were specifically quantified and compared with betaproteobacterial ammonia-oxidizing bacteria (beta-AOB) amoA genes at 150 m; these AOA groups were found to strongly co-vary in time (r(2) = 0.70, P < 0.001) whereas AOA : beta-AOB ratios ranged from 13 to 5630. Increases in the AOA : beta-AOB ratio correlated with the accumulation of nitrite (r(2) = 0.87, P < 0.001), and may be indicative of differences in substrate affinities and activities leading to periodic decoupling between ammonia and nitrite oxidation. These data capture a dynamic nitrogen cycle in which multiple microbial groups appear to be active participants.

  1. Taurine and platelet aggregation

    SciTech Connect

    Nauss-Karol, C.; VanderWende, C.; Gaut, Z.N.

    1986-03-01

    Taurine is a putative neurotransmitter or neuromodulator. The endogenous taurine concentration in human platelets, determined by amino acid analysis, is 15 ..mu..M/g. In spite of this high level, taurine is actively accumulated. Uptake is saturable, Na/sup +/ and temperature dependent, and suppressed by metabolic inhibitors, structural analogues, and several classes of centrally active substances. High, medium and low affinity transport processes have been characterized, and the platelet may represent a model system for taurine transport in the CNS. When platelets were incubated with /sup 14/C-taurine for 30 minutes, then resuspended in fresh medium and reincubated for one hour, essentially all of the taurine was retained within the cells. Taurine, at concentrations ranging from 10-1000 ..mu..M, had no effect on platelet aggregation induced by ADP or epinephrine. However, taurine may have a role in platelet aggregation since 35-39% of the taurine taken up by human platelets appears to be secreted during the release reaction induced by low concentrations of either epinephrine or ADP, respectively. This release phenomenon would imply that part of the taurine taken up is stored directly in the dense bodies of the platelet.

  2. Fractal dimensions and porosities of Zoogloea ramigera and Saccharomyces cerevisae aggregates.

    PubMed

    Logan, B E; Wilkinson, D B

    1991-08-05

    The fractal nature microbial aggregates is a function of the type of microorganism and mixing conditions used to develop aggregates. We determined fractal dimensions from length-projected area (D(2)) and length-number scaling (D(3)) relationships. Aggregates of Zoogloea ramigera developed in rotating test tubes were both surface and mass fractals, with fractal dimensions of D(2) = 1.69 +/- 0.11 and D(3)= 1.79 +/- 0.28 (+/-standard deviation), respectively. When we grew this bacteria in a bench-top fermentor, aggregates maintained their surface fractal characteristics (D(2) = 1.78 +/- 0.11) but lost their mass fractal characteristics (D(3) = 2.99 +/- 0.36). Yeast aggregates (Saccharomyces cerevisae) grown in rotating tests tubes had higher average fractal dimensions than bacterial aggregates grown under physically identical conditions, and were also considered fractal (D(2) = 1.92 +/- 0.08 and D(3) = 2.66 +/- 0.34). Aggregates porosity can be expressed in term of a fractal dimensions, but average porosities are higher than expected. The porosities of yeast aggregates (0.9250-0.9966) were similar to porosities of bacterial aggregates (0.9250-0.9966) cultured under the same physical conditions, although bacterial aggregates developed in the reactor had higher average porosities (0.9857-0.9980). These results suggest that that scaling relationships based on fractal geometry may be more useful than equations derived from Euclidean geometry for quantifying the effects of different fluid mechanical environments on aggregates morphology and characteristics such as density, porosity, and projected surface area.

  3. Titanium dioxide nanoparticles strongly impact soil microbial function by affecting archaeal nitrifiers

    PubMed Central

    Simonin, Marie; Richaume, Agnès; Guyonnet, Julien P.; Dubost, Audrey; Martins, Jean M. F.; Pommier, Thomas

    2016-01-01

    Soils are facing new environmental stressors, such as titanium dioxide nanoparticles (TiO2-NPs). While these emerging pollutants are increasingly released into most ecosystems, including agricultural fields, their potential impacts on soil and its function remain to be investigated. Here we report the response of the microbial community of an agricultural soil exposed over 90 days to TiO2-NPs (1 and 500 mg kg−1 dry soil). To assess their impact on soil function, we focused on the nitrogen cycle and measured nitrification and denitrification enzymatic activities and by quantifying specific representative genes (amoA for ammonia-oxidizers, nirK and nirS for denitrifiers). Additionally, diversity shifts were examined in bacteria, archaea, and the ammonia-oxidizing clades of each domain. With strong negative impacts on nitrification enzyme activities and the abundances of ammonia-oxidizing microorganism, TiO2-NPs triggered cascading negative effects on denitrification enzyme activity and a deep modification of the bacterial community structure after just 90 days of exposure to even the lowest, realistic concentration of NPs. These results appeal further research to assess how these emerging pollutants modify the soil health and broader ecosystem function. PMID:27659196

  4. Nitrogen removal and nitrifying and denitrifying bacteria quantification in a stormwater bioretention system.

    PubMed

    Chen, Xiaolu; Peltier, Edward; Sturm, Belinda S M; Young, C Bryan

    2013-03-15

    In this study, we examine the biological processes involved in ammonia and nitrate removal in a bioretention system characterized by low infiltration rates and long drainage times. The system removed 33% of influent nitrate and 56% of influent total nitrogen. While influent ammonia concentrations were low (<0.3 mg/L), the bioretention cell also removed ammonia produced within the treatment system. Soil cores collected from the bioretention cell were analyzed for total 16S rDNA and both nitrification and denitrification genes (amoA, nirS, nirK, norB, and nosZ) using quantitative PCR. Total bacterial 16S rDNA levels in the surface layer were similar to those in very sandy soils. Gene counts for both nitrification and denitrification genes decreased as a function of depth in the media, and corresponded to similar changes in total 16S rDNA. The abundance of denitrification genes was also positively correlated with the average inundation time at each sampling location, as determined by modeling of stormwater data from a three-year period. These results suggest that both nitrification and denitrification can occur in bioretention media. Time of saturation, filter medium, and organic carbon content can all affect the extent of denitrification in bioretention systems.

  5. Titanium dioxide nanoparticles strongly impact soil microbial function by affecting archaeal nitrifiers

    NASA Astrophysics Data System (ADS)

    Simonin, Marie; Richaume, Agnès; Guyonnet, Julien P.; Dubost, Audrey; Martins, Jean M. F.; Pommier, Thomas

    2016-09-01

    Soils are facing new environmental stressors, such as titanium dioxide nanoparticles (TiO2-NPs). While these emerging pollutants are increasingly released into most ecosystems, including agricultural fields, their potential impacts on soil and its function remain to be investigated. Here we report the response of the microbial community of an agricultural soil exposed over 90 days to TiO2-NPs (1 and 500 mg kg‑1 dry soil). To assess their impact on soil function, we focused on the nitrogen cycle and measured nitrification and denitrification enzymatic activities and by quantifying specific representative genes (amoA for ammonia-oxidizers, nirK and nirS for denitrifiers). Additionally, diversity shifts were examined in bacteria, archaea, and the ammonia-oxidizing clades of each domain. With strong negative impacts on nitrification enzyme activities and the abundances of ammonia-oxidizing microorganism, TiO2-NPs triggered cascading negative effects on denitrification enzyme activity and a deep modification of the bacterial community structure after just 90 days of exposure to even the lowest, realistic concentration of NPs. These results appeal further research to assess how these emerging pollutants modify the soil health and broader ecosystem function.

  6. Nitrifying-denitrifying filters and UV-C disinfection reactor: a combined system for wastewater treatment.

    PubMed

    Ben Rajeb, Asma; Mehri, Inès; Nasr, Houda; Najjari, Afef; Saidi, Neila; Hassen, Abdennaceur

    2017-03-01

    Biological treatment systems use the natural processes of ubiquitous organisms to remove pollutants and improve the water quality before discharge to the environment. In this paper, the nitrification/denitrification reactor allowed a reduction in organic load, but offered a weak efficiency in nitrate reduction. However, the additions of the activated sludge in the reactor improve this efficiency. A decrease of [Formula: see text] values from 13.3 to 8 mg/l was noted. Nevertheless, sludge inoculation led to a net increase of the number of pathogenic bacteria. For this reason, a UV-C pilot reactor was installed at the exit of the biological nitrification-denitrification device. Thus, a fluence of 50 mJ.cm(-2) was sufficient to achieve values of 20 MPN/100 ml for fecal coliform and 6 MPN/100 ml for fecal streptococci, conforms to Tunisian Standards of Rejection. On the other hand, the DGGE approach has allowed a direct assessment of the bacterial community changes upon the treated wastewater.

  7. Stratification of Extracellular Polymeric Substances (EPS) for Aggregated Anammox Microorganisms.

    PubMed

    Jia, Fangxu; Yang, Qing; Liu, Xiuhong; Li, Xiyao; Li, Baikun; Zhang, Liang; Peng, Yongzhen

    2017-03-21

    Sludge aggregation and biofilm formation are the most effective approaches to solve the washout of anammox microorganisms. In this study, the structure and composition of EPS (extracellular polymeric substances) were investigated to elucidate the factors for the anammox aggregation property. Anammox sludge taken from 18 lab-scale and pilot-scale reactors treating different types of wastewater was analyzed using EEM-PARAFAC (excitation-emission matrix and parallel factor analysis), FTIR (Fourier transform infrared spectroscopy) and real-time PCR combined with multivariate statistical analysis. The results showed that slime and TB-EPS (tightly bound EPS) were closely related with water quality and sludge morphology, and could be used as the indicators for anammox microbial survival ability and microbial aggregate morphology. Furthermore, slime secreted from anammox bacterial cells may be exhibited higher viscosity to the sludge surface and easily formed the gel network to aggregate. Large amounts of hydrophobic groups of protein in TB-EPS promoted the microbial aggregation. The mechanisms of anammox aggregation explored in this study enhanced the understanding of anammox stability in wastewater treatment processes.

  8. [Bacterial vaginosis].

    PubMed

    Jesús De La Calle, Iría; Jesús De La Calle, M Antonia

    2009-11-28

    Bacterial vaginosis is a widely spread health problem with multiple connotations. It has been the subject of many studies and work during decades and it still remains a polemic entity, with contradictory finding. The polymicrobian etiology, unsolved epidemiology, obstetrico-gynecological complications and high recurrence rate following treatment, make this infection a target for researchers. It is not an inflammatory process -yet an immune response exists. In this disorder, vaginal discharge increases, and it is associated with a high risk of developing sexually transmitted diseases.

  9. Holographic characterization of protein aggregates

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhong, Xiao; Ruffner, David; Stutt, Alexandra; Philips, Laura; Ward, Michael; Grier, David

    Holographic characterization directly measures the size distribution of subvisible protein aggregates in suspension and offers insights into their morphology. Based on holographic video microscopy, this analytical technique records and interprets holograms of individual aggregates in protein solutions as they flow down a microfluidic channel, without requiring labeling or other exceptional sample preparation. The hologram of an individual protein aggregate is analyzed in real time with the Lorenz-Mie theory of light scattering to measure that aggregate's size and optical properties. Detecting, counting and characterizing subvisible aggregates proceeds fast enough for time-resolved studies, and lends itself to tracking trends in protein aggregation arising from changing environmental factors. No other analytical technique provides such a wealth of particle-resolved characterization data in situ. Holographic characterization promises accelerated development of therapeutic protein formulations, improved process control during manufacturing, and streamlined quality assurance during storage and at the point of use. Mrsec and MRI program of the NSF, Spheryx Inc.

  10. Secreted protease mediates interspecies interaction and promotes cell aggregation of the photosynthetic bacterium Chloroflexus aggregans.

    PubMed

    Morohoshi, Sho; Matsuura, Katsumi; Haruta, Shin

    2015-01-01

    Interspecies interactions were studied in hot spring microbial mats where diverse species of bacterial cells are densely packed. The anoxygenic photosynthetic bacterium, Chloroflexus aggregans, has been widely found in the microbial mats as a major component in terrestrial hot springs in Japan at the temperature from 50 to 70°C. C. aggregans shows cellular motility to form a microbial mat-like dense cell aggregate. The aggregating ability of C. aggregans was affected by another bacterial species, strain BL55a (related to Bacillus licheniformis) isolated from the microbial mats containing C. aggregans. Cell aggregation rate of C. aggregans was promoted by the addition of culture supernatants of strain BL55a. Similar effects were also detected from other bacterial isolates, specifically Geobacillus sp. and Aeribacillus sp. Protease activity was detected from the culture supernatants from all of these isolates. The promoting effect of strain BL55a was suppressed by a serine protease inhibitor, phenylmethylsulfonyl fluoride. A purified serine protease, subtilisin obtained from B. licheniformis, showed a promoting effect on the cell aggregation. These results suggest that an extracellular protease, secreted from co-existing bacterial species promoted the aggregating motility of C. aggregans. This is the first report that exogenous protease affects bacterial cellular motility.

  11. Solving Transportation Problems via Aggregation,

    DTIC Science & Technology

    1984-07-01

    AD-A144 219 SOLVING TRANSPORTATION PROBLEMS VIA AGGREGATION (U) i/l GEORGIA INST OF TECH ATLANTA PRODUCTION AND DISTRIBUTION RESEARCH CENTER R W...10 July 1984 SOLVING TRANSPORTATION PROBLEMS VIA AGGREGATION by" 4 Richard W. Taylort C. M. Shettytt PDRC 84-10 DTIC E L - TE~ School of Business...c UoaOO48--17 Rpouto spritein whol or pr for ny prpos of he U S. overment Abstract Solving Transportation Problems Via Aggregation 0

  12. Establishment and early succession of bacterial communities in monochloramine-treated drinking water biofilms.

    PubMed

    Revetta, Randy P; Gomez-Alvarez, Vicente; Gerke, Tammie L; Curioso, Claudine; Santo Domingo, Jorge W; Ashbolt, Nicholas J

    2013-12-01

    Monochloramine is an increasingly used drinking water disinfectant and has been shown to increase nitrifying bacteria and mycobacteria in drinking waters. The potential successions and development of these bacteria were examined by 16S rRNA gene clone libraries generated from various biofilms within a water distribution system simulator. Biofilms were obtained from in-line and off-line devices using borosilicate glass beads, along with polycarbonate coupons from annular reactors incubated for up to 8 months in monochloramine-treated drinking water. No significant difference in community structures was observed between biofilm devices and coupon material; however, all biofilm communities that developed on different devices underwent similar successions over time. Early stages of biofilm formation were dominated by Serratia (29%), Cloacibacterium (23%), Diaphorobacter (16%), and Pseudomonas (7%), while Mycobacterium-like phylotypes were the most predominant populations (> 27%) in subsequent months. The development of members of the nontuberculous mycobacteria (NTM) after 3 months may impact individuals with predisposing conditions, while nitrifiers (related to Nitrospira moscoviensis and Nitrosospira multiformis) could impact water quality. Overall, 90% of the diversity in all the clone library samples was associated with the phyla Proteobacteria, Actinobacteria, and Bacteroidetes. These results provide an ecological insight into biofilm bacterial successions in monochloramine-treated drinking water.

  13. The structure of microbial community in aggregates of a typical chernozem aggregates under contrasting variants of its agricultural use

    NASA Astrophysics Data System (ADS)

    Ivanova, E. A.; Kutovaya, O. V.; Tkhakakhova, A. K.; Chernov, T. I.; Pershina, E. V.; Markina, L. G.; Andronov, E. E.; Kogut, B. M.

    2015-11-01

    The taxonomic structure of microbiomes in aggregates of different sizes from typical chernozems was investigated using sequencing of the 16S rRNA gene. The aggregate fractions of <0.25, 2-5, and >7 mm obtained by sieving of the soil samples at natural moisture were used for analysis. The highest prokaryote biomass (bacteria, archaea) was determined in the fractions <0.25 and aggregates 2-5 mm; the bacterial and archaeal biomass decreased in the following series: fallow > permanent black fallow > permanent winter wheat. The greatest number of fungi was recorded in the fraction <0.25 mm from the soils of the permanent black fallow and in all the studied aggregate fractions in the variant with permanent wheat. The system of agricultural use affected more significantly the structure of the prokaryote community in the chernozem than the size of aggregate fractions did. The most diverse microbial community was recorded in the soil samples of the fallow; the statistically significant maximums of the Shannon diversity indices and indices of phylogenetic diversity (PD) were recorded in the fractions <0.25 and 2-5 mm from the fallow soil. On the whole, the fine soil fractions (<0.25 mm) were characterized by higher diversity indices in comparison with those of the coarser aggregate fractions.

  14. Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor

    PubMed Central

    Langone, Michela; Yan, Jia; Haaijer, Suzanne C. M.; Op den Camp, Huub J. M.; Jetten, Mike S. M.; Andreottola, Gianni

    2014-01-01

    Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale sequencing batch reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of 8.0 and 7.8–8.0, respectively. Short term effect of nitrite on anammox activity was studied, showing nitrite up to 42 mg/L did not result in inhibition. Both denitrification via nitrate and nitrite were measured. To reduce nitrite-oxidizing activity, high NH3-N (1.9–10 mg NH3-N/L) and low nitrite (3–8 mg TNN/L) are required conditions during the whole SBR cycle. Molecular analysis showed the nitritation-anammox sludge harbored a high microbial diversity, where each microorganism has a specific role. Using ammonia monooxygenase α–subunit (amoA) gene as a marker, our analyses suggested different macro- and micro-environments in the reactor strongly affect the AOB community, allowing the development of different AOB species, such as N. europaea/eutropha and N. oligotropha groups, which improve the stability of nitritation process. A specific PCR primer set, used to target the 16S rRNA gene of anammox bacteria, confirmed the presence of the “Ca. Brocadia fulgida” type, able to grow in presence of organic matter and to tolerate high nitrite concentrations. The diversity of denitrifiers was assessed by using dissimilatory nitrite reductase (nirS) gene-based analyses, who showed denitifiers were related to different betaproteobacterial genera, such as Thauera, Pseudomonas, Dechloromonas and Aromatoleum, able to assist in forming microbial aggregates. Concerning possible secondary processes, no n-damo bacteria were found while NOB from the genus Nitrobacter was detected

  15. Isotope investigations of nitrification dynamics in the Elbe River and in pure cultures of nitrifying bacteria

    NASA Astrophysics Data System (ADS)

    Jacob, Juliane; Sanders, Tina; Dähnke, Kirstin

    2013-04-01

    Since the onset of industrialisation, the nutrient input to aquatic systems is significally enhanced. This leads to high nitrogen loads in rivers, which drain densely populated catchments, and an increased eutrophication pressure on coastal water bodies. Along the river - estuary - continuum, nitrogen processing in aquatic environments has the potential to alter river loads significantly. Especially nitrification, the stepwise oxidation of ammonium to nitrite and further to nitrate, is important, because it can create additional nitrate from freshly remineralized organic matter, but also represents the link to subsequent removal via denitrification. Stable isotopes are a valuable tool to track overlapping source and sink processes in natural environments: Changes in stable isotope ratios can be attributed to the corresponding turnover processes, if the corresponding isotope effects are carefully assessed. However, the data base on N and O isotope fractionation in natural environments and during specific turnover processes is scarce. Thus we aimed to better understand the isotope dynamics of nitrification, assigning specific fractionation factors to environmentally relevant bacterial species. Besides N and O isotope analyses of river nitrate over an annual cycle, we performed incubation experiments with pure cultures and river water. Biweekly water samples from the Elbe River (Northern Germany) were taken to analyse, among other parameters, the seasonal variations of δ15N and δ18O in nitrate, corresponding nitrification rates and isotope effects during nitrification. While changes in δ15N and δ18O suggest phytoplankton assimilation as the main turnover process, incubations of river water reveal the relevance of nutrient regeneration via nitrification, which increase 15-fold with the onset of spring. In these incubations, we analysed rates of ammonium and nitrite oxidation and the corresponding isotope fractionation factors. Additional experiments with newly

  16. Aggregation dynamics of rigid polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Tom, Anvy Moly; Rajesh, R.; Vemparala, Satyavani

    2016-01-01

    Similarly charged polyelectrolytes are known to attract each other and aggregate into bundles when the charge density of the polymers exceeds a critical value that depends on the valency of the counterions. The dynamics of aggregation of such rigid polyelectrolytes are studied using large scale molecular dynamics simulations. We find that the morphology of the aggregates depends on the value of the charge density of the polymers. For values close to the critical value, the shape of the aggregates is cylindrical with height equal to the length of a single polyelectrolyte chain. However, for larger values of charge, the linear extent of the aggregates increases as more and more polymers aggregate. In both the cases, we show that the number of aggregates decrease with time as power laws with exponents that are not numerically distinguishable from each other and are independent of charge density of the polymers, valency of the counterions, density, and length of the polyelectrolyte chain. We model the aggregation dynamics using the Smoluchowski coagulation equation with kernels determined from the molecular dynamics simulations and justify the numerically obtained value of the exponent. Our results suggest that once counterions condense, effective interactions between polyelectrolyte chains short-ranged and the aggregation of polyelectrolytes are diffusion-limited.

  17. Fractal structure of asphaltene aggregates.

    PubMed

    Rahmani, Nazmul H G; Dabros, Tadeusz; Masliyah, Jacob H

    2005-05-15

    A photographic technique coupled with image analysis was used to measure the size and fractal dimension of asphaltene aggregates formed in toluene-heptane solvent mixtures. First, asphaltene aggregates were examined in a Couette device and the fractal-like aggregate structures were quantified using boundary fractal dimension. The evolution of the floc structure with time was monitored. The relative rates of shear-induced aggregation and fragmentation/restructuring determine the steady-state floc structure. The average floc structure became more compact or more organized as the floc size distribution attained steady state. Moreover, the higher the shear rate is, the more compact the floc structure is at steady state. Second, the fractal dimensions of asphaltene aggregates were also determined in a free-settling test. The experimentally determined terminal settling velocities and characteristic lengths of the aggregates were utilized to estimate the 2D and 3D fractal dimensions. The size-density fractal dimension (D(3)) of the asphaltene aggregates was estimated to be in the range from 1.06 to 1.41. This relatively low fractal dimension suggests that the asphaltene aggregates are highly porous and very tenuous. The aggregates have a structure with extremely low space-filling capacity.

  18. Peptide Aggregation in Finite Systems

    PubMed Central

    Singh, Gurpreet; Brovchenko, Ivan; Oleinikova, Alla; Winter, Roland

    2008-01-01

    Universal features of the peptide aggregation process suggest a common mechanism, with a first-order phase transition in aqueous solutions of the peptides being the driving force. Small system sizes strongly affect the stability of the minor phase in the two-phase region. We show manifestations of this effect in aqueous solutions of fragments of the islet amyloid polypeptide, using computer simulation methods and invoking various approaches in characterizing clustering and aggregate formation. These systems with peptide concentrations deeply inside the immiscibility region show two distinct stable states, which interchange with time: one state contains a peptide aggregate; and the other state has an aggregate that is noticeably dissolved. The first state is relevant for macroscopic systems, whereas the second one is artificial. At a fixed concentration, the occurrence probability of the aggregate state vanishes upon decreasing the system size, thus indicating the necessity to apply a finite size-scaling for meaningful studies of peptide aggregation by simulations. The effect observed may be one of the factors responsible for the difference between intracellular and extracellular aggregation and fibrillization of polypeptides. The finite size of biological cells or their compartments may be playing a decisive role in hampering intracellular aggregation of highly insoluble amyloidogenic proteins, whereas aggregation is unavoidable in the extracellular space at the same peptide concentration. PMID:18621830

  19. Molecular Aggregates in Cryogenic Solutions.

    DTIC Science & Technology

    1981-07-07

    of aggregates from solutions of monomers. Rapid deposition into a precooled sample cell is required to generate an aggregate solution. Such a solution...U AU-A11b 490 COLORAO0 STATE UNIV FORT COLLINS DEPT OF CHEMISTRY F/G 20/8 MOLECULAR AGGREGATES IN CRYOGENIC SOLUTIONS.CU) JUL 81 M W SCHAUER- J LEE...MOLECULAR AGGREGATES IN CRYOGENIC SOLUTIONS by M.W. Schauer, J. Lee, and E.R. Bernstein Prepared for Publication in The Journal of Chemical Physics

  20. Failure of bacterial streamers in creeping flows

    NASA Astrophysics Data System (ADS)

    Biswas, Ishita; Ghosh, Ranajay; Sadrzadeh, Mohtada; Kumar, Aloke

    2016-11-01

    In the recent years, the dynamical response of filamentous bacterial aggregates called bacterial streamer in creeping flows has attracted attention. We report the observation of 'necking-type' instability leading to failure in bacterial (Pseudomonas fluorescens) streamers formed in creeping flows. Quantification of the failure process was made possible through the use of 200 nm red fluorescent polystyrene tracer particles embedded in the bacterial extracellular polymeric substances (EPS). The nonlinear failure behavior shows distinct phases of deformation with mutually different characteristic times, which end with a distinct localized failure of the streamer. We also develop a simplified analytical model to describe the experimental observations of the failure phenomena. The theoretical power law relationship between critical stretch ratio and the fluid velocity scale matches closely experimental observations.

  1. Ammonium removal of drinking water at low temperature by activated carbon filter biologically enhanced with heterotrophic nitrifying bacteria.

    PubMed

    Qin, Wen; Li, Wei-Guang; Zhang, Duo-Ying; Huang, Xiao-Fei; Song, Yang

    2016-03-01

    We sought to confirm whether use of Acinetobacter strains Y7 and Y16, both strains of heterotrophic nitrifying bacteria, was practical for removing ammonium (NH4 (+)-N) from drinking water at low temperatures. To test this, ammonium-containing drinking water was treated with strains Y7 and Y16 at 8 and 2 °C. Continuous ammonium treatment was conducted in order to evaluate the performance of three biologically enhanced activated carbon (BEAC) filters in removing ammonium. The three BEAC filters were inoculated with strain Y7, strain Y16, and a mixture of strains Y7 and Y16, respectively. A granular activated carbon (GAC) filter, without inoculation by any strains, was tested in parallel with the BEAC filters as control. The results indicated that NH4 (+)-N removal was significant when a BEAC filter was inoculated with the mixture of strains Y7 and Y16 (BEAC-III filter). Amounts of 0.44 ± 0.05 and 0.25 ± 0.05 mg L(-1) NH4 (+)-N were removed using the BEAC-III filter at 8 and 2 °C, respectively. These values were 2.8-4.0-fold higher than the values of ammonium removal acquired using the GAC filter. The synergistic effect of using strains Y7 and Y16 in concert was the cause of the high-ammonium removal efficiency achieved by using the BEAC-III filter at low temperatures. In addition, a high C/N ratio may promote NH4 (+)-N removal efficiency by improving biomass and microbial activity. This study provides new insight into the use of biofilters to achieve biological removal of ammonium at low temperature.

  2. The effect of dissolved oxygen on N2O production by ammonia-oxidizing bacteria in an enriched nitrifying sludge.

    PubMed

    Peng, Lai; Ni, Bing-Jie; Erler, Dirk; Ye, Liu; Yuan, Zhiguo

    2014-12-01

    Dissolved oxygen (DO) is commonly recognized as an important factor influencing nitrous oxide (N2O) production by ammonia-oxidizing bacteria (AOB). However, it has been difficult to separate the true effect of DO from that of nitrite, as DO variation often affects nitrite accumulation. The effect of DO on N2O production by an enriched nitrifying sludge, consisting of both AOB and nitrite-oxidizing bacteria (NOB), was investigated in this study. Nitrite accumulation was minimised by augmenting nitrite oxidation through the addition of an enriched NOB sludge. It was demonstrated that the specific N2O production rate increased from 0 to 1.9 ± 0.09 (n = 3) mg N2O-N/hr/g VSS with an increase of DO concentration from 0 to 3.0 mg O2/L, whereas N2O emission factor (the ratio between N2O nitrogen emitted and the ammonium nitrogen converted) decreased from 10.6 ± 1.7% (n = 3) at DO = 0.2 mg O2/L to 2.4 ± 0.1% (n = 3) at DO = 3.0 mg O2/L. The site preference measurements indicated that both the AOB denitrification and hydroxylamine (NH2OH) oxidation pathways contributed to N2O production, and DO had an important effect on the relative contributions of the two pathways. This finding is supported by analysis of the process data using an N2O model describing both pathways. As DO increased from 0.2 to 3.0 mg O2/L, the contribution of AOB denitrification decreased from 92% - 95%-66% - 73%, accompanied by a corresponding increase in the contribution by the NH2OH oxidation pathway. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Impact of microbial physiology and microbial community structure on pharmaceutical fate driven by dissolved oxygen concentration in nitrifying bioreactors.

    PubMed

    Stadler, Lauren B; Love, Nancy G

    2016-11-01

    Operation at low dissolved oxygen (DO) concentrations (<1 mg/L) in wastewater treatment could save utilities significantly by reducing aeration energy costs. However, few studies have evaluated the impact of low DO on pharmaceutical biotransformations during treatment. DO concentration can impact pharmaceutical biotransformation rates during wastewater treatment both directly and indirectly: directly by acting as a limiting substrate that slows the activity of the microorganisms involved in biotransformation; and indirectly by shaping the microbial community and selecting for a community that performs pharmaceutical biotransformation faster (or slower). In this study, nitrifying bioreactors were operated at low (∼0.3 mg/L) and high (>4 mg/L) DO concentrations to understand how DO growth conditions impacted microbial community structure. Short-term batch experiments using the biomass from the parent reactors were performed under low and high DO conditions to understand how DO concentration impacts microbial physiology. Although the low DO parent biomass had a lower specific activity with respect to ammonia oxidation than the high DO parent reactor biomass, it had faster biotransformation rates of ibuprofen, sulfamethoxazole, 17α-ethinylestradiol, acetaminophen, and atenolol in high DO batch conditions. This was likely because the low DO reactor had a 2x higher biomass concentration, was enriched for ammonia oxidizers (4x higher concentration), and harbored a more diverse microbial community (3x more unique taxa) as compared to the high DO parent reactor. Overall, the results show that there can be indirect benefits from low DO operation over high DO operation that support pharmaceutical biotransformation during wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Nitrous oxide emissions and dissolved oxygen profiling in a full-scale nitrifying activated sludge treatment plant.

    PubMed

    Aboobakar, Amina; Cartmell, Elise; Stephenson, Tom; Jones, Mark; Vale, Peter; Dotro, Gabriela

    2013-02-01

    This paper reports findings from online, continuous monitoring of dissolved and gaseous nitrous oxide (N₂O), combined with dissolved oxygen (DO) and ammonia loading, in a full-scale nitrifying activated sludge plant. The study was conducted over eight weeks, at a 210,000 population equivalent sewage treatment works in the UK. Results showed diurnal variability in the gaseous and dissolved N₂O emissions, with hourly averages ranging from 0 to 0.00009 kgN₂O-N/h for dissolved and 0.00077-0.0027 kgN₂O-N/h for gaseous nitrous oxide emissions respectively, per ammonia loading, depending on the time of day. Similarly, the spatial variability was high, with the highest emissions recorded immediately after the anoxic zone and in the final pass of the aeration lane, where ammonia concentrations were typically below 0.5 mg/L. Emissions were shown to be negatively correlated to dissolved oxygen, which fluctuated between 0.5 and 2.5 mgO₂/L, at the control set point of 1.5 mgO₂/L. The resulting dynamic DO conditions are known to favour N₂O production, both by autotrophic and heterotrophic processes in mixed cultures. Average mass emissions from the lane were greater in the gaseous (0.036% of the influent total nitrogen) than in the dissolved (0.01% of the influent total nitrogen) phase, and followed the same diurnal and spatial patterns. Nitrous oxide emissions corresponded to over 34,000 carbon dioxide equivalents/year, adding 13% to the carbon footprint associated with the energy requirements of the monitored lane. A clearer understanding of emissions obtained from real-time data can help towards finding the right balance between improving operational efficiency and saving energy, without increasing N₂O emissions. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Simultaneous removal of carbon and nitrogen by mycelial pellets of a heterotrophic nitrifying fungus-Penicillium sp. L1.

    PubMed

    Liu, Yuxiang; Hu, Tingting; Zhao, Jing; Lv, Yongkang; Ren, Ruipeng

    2017-02-01

    A novel heterotrophic nitrifying fungus, defined as Penicillium sp. L1, can form mycelial pellets in liquid medium in this study. The effects of inoculation method, C/N ratio, initial pH, and temperature were gradually evaluated to improve the simultaneous removal of total nitrogen (TN) and chemical oxygen demand (COD) in wastewater by Penicillium sp. L1. Results showed that compared with spore inoculation, 48 h pellet inoculum could significantly increase the pellet size (from about 1.5 mm to 3.2 mm) and improve the removal capability, particularly for COD removal (from less than 50-86.20%). The removal efficiencies of TN and COD reached 98.38% (from 136.01 mg/L to 2.20 mg/L) and 92.40% (from 10,720 mg/L to 815 mg/L) under the following conditions: C/N 36, pH 3, 30°C, and inoculation with 48 h pellets. The pellet diameter reached 4.8 mm after 4-day cultivation. In this case, Penicillium sp. L1 removed TN from 415.93 mg/L to 43.39 mg/L, as well as COD from 29,533 mg/L to 8850 mg/L. Overall, the results indicated that the pellet size was closely related to the pollutant-removal ability of Penicillium sp. L1. Furthermore, mycelial pellets (4.8 mm, dead) only adsorbed 38.08% TN (from 125.45 mg/L to 77.78 mg/L), which indicated that adsorption did not play a major role in the nitrogen-removal process. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  6. Brevibacillus nitrificans sp. nov., a nitrifying bacterium isolated from a microbiological agent for enhancing microbial digestion in sewage treatment tanks.

    PubMed

    Takebe, Fumihiko; Hirota, Kikue; Nodasaka, Yoshinobu; Yumoto, Isao

    2012-09-01

    A heterotrophic nitrifying bacterium, designated strain DA2(T), was isolated from a microbiological agent for enhancing microbial digestion in sewage treatment tanks. Cells of strain DA2(T) were Gram-positive, facultatively anaerobic, sporulating rods that were motile by means of peritrichous flagella; they were able to grow at pH 5-8. The major isoprenoid quinone of strain DA2(T) was menaquinone-7 (MK-7) and its cellular fatty acid profile consisted mainly of iso-C(15 : 0) (18.6 %) and anteiso-C(15 : 0) (69.1 %). The DNA G+C content was 54.1 mol%. 16S rRNA gene sequence phylogeny suggested that strain DA2(T) is a member of the genus Brevibacillus, with highest sequence similarities (in parentheses) to the type strains of Brevibacillus choshinensis (99.7 %), B. formosus (99.4 %), B. brevis (99.4 %), B. agri (99.0 %), B. reuszeri (98.8 %), B. parabrevis (98.7 %), B. centrosporus (98.6 %), B. limnophilus (97.4 %), B. panacihumi (97.3 %) and B. invocatus (97.3 %). DNA-DNA hybridization showed less than 60 % relatedness between strain DA2(T) and type strains of the most closely related species given above. Given the significant differences in phenotypic and chemotaxonomic characteristics, and phylogenetic analysis based on the 16S rRNA sequence and DNA-DNA relatedness data, the isolate merits classification as a novel species, for which the name Brevibacillus nitrificans is proposed; the type strain of this species is DA2(T) (= JCM 15774(T) = NCIMB 14531(T)).

  7. Archaeal ammonia oxidizers and nirS-type denitrifiers dominate sediment nitrifying and denitrifying populations in a subtropical macrotidal estuary.

    PubMed

    Abell, Guy C J; Revill, Andrew T; Smith, Craig; Bissett, Andrew P; Volkman, John K; Robert, Stanley S

    2010-02-01

    Nitrification and denitrification are key steps in nitrogen (N) cycling. The coupling of these processes, which affects the flow of N in ecosystems, requires close interaction of nitrifying and denitrifying microorganisms, both spatially and temporally. The diversity, temporal and spatial variations in the microbial communities affecting these processes was examined, in relation to N cycling, across 12 sites in the Fitzroy river estuary, which is a turbid subtropical estuary in central Queensland. The estuary is a major source of nutrients discharged to the Great Barrier Reef near-shore zone. Measurement of nitrogen fluxes showed an active denitrifying community during all sampling months. Archaeal ammonia monooxygenase (amoA of AOA, functional marker for nitrification) was significantly more abundant than Betaproteobacterial (beta-AOB) amoA. Nitrite reductase genes, functional markers for denitrification, were dominated by nirS and not nirK types at all sites during the year. AOA communities were dominated by the soil/sediment cluster of Crenarchaeota, with sequences found in estuarine sediment, marine and terrestrial environments, whereas nirS sequences were significantly more diverse (where operational taxonomic units were defined at both the threshold of 5% and 15% sequence similarity) and were closely related to sequences originating from estuarine sediments. Terminal-restriction fragment length polymorphism (T-RFLP) analysis revealed that AOA population compositions varied spatially along the estuary, whereas nirS populations changed temporally. Statistical analysis of individual T-RF dominance suggested that salinity and C:N were associated with the community succession of AOA, whereas the nirS-type denitrifier communities were related to salinity and chlorophyll-alpha in the Fitzroy river estuary.

  8. The synergistic effects of dissolved oxygen and pH on N2O production in biological domestic wastewater treatment under nitrifying conditions.

    PubMed

    Li, Pengzhang; Wang, Shuying; Peng, Yongzhen; Liu, Yue; He, Janzhong

    2015-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas, which is produced during nitrifying and denitrifying processes. Some factors and mechanisms affecting N2O emission have been reported in previous literature, but wastewater biological nitrification is accompanied by a dynamic process of dissolved oxygen (DO) consumption and pH reduction, it is more meaningful to study the synergistic effects between DO and pH on N2O production. In this study, the synergistic effects between DO and pH on N2O production were investigated with real domestic wastewater. The results showed that high DO levels and a high pH could improve the oxidation ratio of NH4+-N and the production ratio of NO2--N, while effectively reducing the accumulation ratio of N2O. The NH4+-N was a prerequisite for nitrifier denitrification; when NH4+-N was oxidized completely, there would be no N2O production and an even higher concentration of NO2- The pH factor is shown to directly affect N2O emission, although free ammonia and free nitrous acid which changed with pH had no correlation with N2O emission. There were two reasons: (1) pH can influence the flow direction of electrons afforded by NH2OH oxidation; at high pH, electrons were mainly used for combining H+ and O2 (O2+4H++4e-=2H2O), the accumulation of NO2- cannot be a result of denitrification, and a higher DO can get more electrons to prefer NO2- and (2) NH4+ was the prerequisite for NH2OH oxidation, since NH2OH oxidation process was the way to provide electrons for nitrifier denitrification.

  9. Microbial ecology and performance of nitrifying bacteria in an aerobic membrane bioreactor treating thin-film transistor liquid crystal display wastewater.

    PubMed

    Whang, L M; Yang, Y F; Huang, S J; Cheng, S S

    2008-01-01

    This study was conducted to evaluate the long-term performance of an aerobic membrane bioreactor (MBR), treating TFT-LCD wastewater containing dimethyl sulphoxide (DMSO), monoethanolamine (MEA) and tetra-methyl ammonium hydroxide (TMAH), which are recognized as slow-biodegradable organic compounds containing nitrogen and can release significant amount of ammonia during biodegradation. Moreover, many studies have reported that certain organic compounds can potentially inhibit nitrification of AOB, but limited information is available regarding the effects of TFT-LCD wastewater compounds on nitrification performance and microbial ecology of nitrifying bacteria. In general, the aerobic MBR achieved satisfactory conversion efficiency for DMSO, MEA, TMAH, and ammonia, except that a sudden inhibition on MEA degradation was observed for a transition period when the influent feed switched from synthetic to real TFT-LCD wastewater. Furthermore, the terminal restriction fragment length polymorphism (T-RFLP) methodology was applied to monitor the microbial ecology of nitrifying bacteria in the aerobic MBR. The results suggested that Nm. marina or Nm. cummunis were the dominant AOB population in the aerobic MBR fed with synthetic TFT-LCD wastewater, while Nitrosospira became dominant in the aerobic MBR fed with real TFT-LCD wastewater. For the NOB population, both Nitrobacter and Nitrospira were present during this study. Finally, the results of batch experiments, which were conducted to evaluate the effects of DMSO, MEA, and TMAH on nitrification activity, indicated that MEA and TMAH became inhibitory to nitrifying bacteria at concentrations of 250 and 50 mg/L, respectively, while DMSO did not at concentrations up to 100 mg/L. IWA Publishing 2008.

  10. Influence of Biological Macromolecules and Aquatic Chemistries on the Inhibition of Nitrifying Bacteria by Silver Nanoparticles

    NASA Astrophysics Data System (ADS)

    Radniecki, T. S.; Anderson, J. W.; Schneider, M. C.; Stankus, D. P.; Nason, J. A.; Semprini, L.

    2010-12-01

    The use of silver nanoparticles (Ag-NP) as a broad spectrum biocide in a wide range of consumer goods has grown exponentially since 2006 (1), which may result in an increased release of Ag-NP into wastewater streams and ultimately the receiving bodies of water. Ammonia oxidizing bacteria (AOB) play a critical role in the global nitrogen cycle through the oxidation of ammonia (NH3) to nitrite (NO2-) and are widely considered to be the most sensitive microbial fauna in the environment being readily inhibited by contaminants, including Ag-NP (2). This research used physiological techniques in combination with physical/chemical assays to characterize the inhibition of Nitrosomonas europaea, the model AOB, by silver ions (Ag+), 3-5 nm Ag-NP, 20 nm Ag-NP and 80 nm Ag-NP under a variety of aqueous chemistries. In addition, the stability of Ag-NP suspensions was examined under a variety of aqueous chemistries including in the presences of divalent cations, chloride anions, natural organic matter (NOM), proteins (BSA) and lipopolysaccharides (alginate). Using the stable Ag-NP/test media suspensions, N. europaea was found to be extremely sensitive to Ag+, 3-5 nm Ag-NP, 20 nm Ag-NP and 80 nm Ag-NP with concentrations of 0.1, 0.12, 0.5 and 1.5 ppm, respectively, resulting in a 50% decrease in nitrification rates. The inhibition was correlated with the amount of Ag+ released into solution. It is suspected that the inhibition observed from Ag-NP exposure is caused by the liberated Ag+. The aquatic chemistry of the test media was found to have a profound influence on the stability of Ag-NP suspensions. The presence of Ag ligands (e.g. EDTA and Cl-) reduced toxicity of Ag-NP through the formation of Ag-ligand complexes with the liberated Ag+. The presence of divalent cations (e.g. Ca2+ or Mg2+) resulted in the rapid aggregation of Ag-NP leading to a decrease in Ag+ liberation and thus a decrease in N. europaea inhibition. The presence of 5 ppm NOM resulted in a highly stable Ag

  11. Bacterial Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Lauga, Eric

    2016-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells, yet they represent the bulk of the world's biomass and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micrometer scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically complex environments. Using hydrodynamics as an organizing framework, I review the biomechanics of bacterial motility and look ahead to future challenges.

  12. Bacterial vaginosis.

    PubMed

    Priestley, C J; Kinghorn, G R

    1996-09-01

    Bacterial vaginosis (BV) is an alteration of the vaginal flora, where the normally predominant lactobacilli are replaced by a cocktail of organisms including Gardnerella vaginalis and anaerobes. It presents with a grey, homogenous, offensive vaginal discharge that has a raised pH. However, around half the women with this condition are asymptomatic. Diagnosis is best made by microscopic examination of a Gram-stained smear of vaginal secretions. Treatment is with metronidazole or clindamycin. The indications for treatment of asymptomatic BV are not clear, but women should probably be treated before any invasive gynaecological procedure, including intrauterine contraceptive device (IUCD) insertion. BV during pregnancy is associated with preterm labour, although a causal effect is not proven; studies are in progress to determine whether treatment of BV will improve the outcome of these pregnancies.

  13. Bacterial Actins.

    PubMed

    Izoré, Thierry; van den Ent, Fusinita

    2017-01-01

    A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell. FtsA is widespread across bacteria and it is one of the earliest components of the divisome to arrive at midcell, where it anchors the cell division machinery to the membrane. FtsA binds directly to FtsZ filaments and to the membrane through its C-terminus. FtsA shows altered domain architecture when compared to the canonical actin fold. FtsA's subdomain 1C replaces subdomain 1B of other members of the actin family and is located on the opposite side of the molecule. Nevertheless, when FtsA assembles into protofilaments, the protofilament structure is preserved, as subdomain 1C replaces subdomain IB of the following subunit in a canonical actin filament. MreB has an essential role in shape-maintenance of most rod-shaped bacteria. Unusually, MreB filaments assemble from two protofilaments in a flat and antiparallel arrangement. This non-polar architecture implies that both MreB filament ends are structurally identical. MreB filaments bind directly to membranes where they interact with both cytosolic and membrane proteins, thereby forming a key component of the elongasome. MreB filaments in cells are short and dynamic, moving around the long axis of rod-shaped cells, sensing curvature of the membrane and being implicated in peptidoglycan synthesis.

  14. Topics in Probabilistic Judgment Aggregation

    ERIC Educational Resources Information Center

    Wang, Guanchun

    2011-01-01

    This dissertation is a compilation of several studies that are united by their relevance to probabilistic judgment aggregation. In the face of complex and uncertain events, panels of judges are frequently consulted to provide probabilistic forecasts, and aggregation of such estimates in groups often yield better results than could have been made…

  15. Topics in Probabilistic Judgment Aggregation

    ERIC Educational Resources Information Center

    Wang, Guanchun

    2011-01-01

    This dissertation is a compilation of several studies that are united by their relevance to probabilistic judgment aggregation. In the face of complex and uncertain events, panels of judges are frequently consulted to provide probabilistic forecasts, and aggregation of such estimates in groups often yield better results than could have been made…

  16. Mineral of the month: aggregates

    USGS Publications Warehouse

    Tepordei, Valentin V.

    2005-01-01

    Natural aggregates, consisting of crushed stone, and sand and gravel, are a major contributor to economic health, and have an amazing variety of uses. Aggregates are among the most abundant mineral resources and are major basic raw materials used by construction, agriculture and other industries that employ complex chemical and metallurgical processes.

  17. Molecular aggregation of humic substances

    USGS Publications Warehouse

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  18. Imbibition kinetics of spherical aggregates

    NASA Astrophysics Data System (ADS)

    Hébraud, Pascal; Lootens, Didier; Debacker, Alban

    The imbibition kinetics of a millimeter-sized aggregate of 300 nm diameter colloidal particles by a wetting pure solvent is studied. Three successive regimes are observed : in the first one, the imbibition proceeds by compressing the air inside the aggregate. Then, the solvent stops when the pressure of the compressed air is equal to the Laplace pressure at the meniscus of the wetting solvent in the porous aggregate. The interface is pinned and the aggregate slowly degases, up to a point where the pressure of the entrapped air stops decreasing and is controlled by the Laplace pressure of small bubbles. Depending on the curvature of the bubble, the system may then be in an unstable state. The imbibition then starts again, but with an inner pressure in equilibrium with these bubbles. This last stage leads to the complete infiltration of the aggregate.

  19. A revisited folding reporter for quantitative assay of protein misfolding and aggregation in mammalian cells.

    PubMed

    Gregoire, Simpson; Kwon, Inchan

    2012-10-01

    Protein misfolding and aggregation play important roles in many physiological processes. These include pathological protein aggregation in neurodegenerative diseases and biopharmaceutical protein aggregation during production in mammalian cells. To develop a simple non-invasive assay for protein misfolding and aggregation in mammalian cells, the folding reporter green fluorescent protein (GFP) system, originally developed for bacterial cells, was evaluated. As a folding reporter, GFP was fused to the C-terminus of a panel of human copper/zinc superoxide dismutase (SOD1) mutants with varying misfolding/aggregation propensities. Flow cytometric analysis of transfected HEK293T and NSC-34 cells revealed that the mean fluorescence intensities of the cells expressing GFP fusion of SOD1 variants exhibited an inverse correlation with the misfolding/aggregation propensities of the four SOD1 variants. Our results support the hypothesis that the extent of misfolding/aggregation of a target protein in mammalian cells can be quantitatively estimated by measuring the mean fluorescence intensity of the cells expressing GFP fusion. The assay method developed herein will facilitate the understanding of aggregation process of SOD1 variants and the identification of aggregation inhibitors. The method also has great promise for misfolding/aggregation studies of other proteins in mammalian cells. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Premature red blood cells have decreased aggregation and enhanced aggregability.

    PubMed

    Arbell, D; Orkin, B; Bar-Oz, B; Barshtein, G; Yedgar, S

    2008-06-01

    Preterm infants are highly susceptible to ischemic damage. This damage is most obvious in the brain, retina, and gastrointestinal tract. Studies focusing on the rheological properties of premature red blood cells (pRBCs) have consistently shown minimal or no RBC aggregation. Previously, measurements of pRBC aggregation kinetics indicated that specific plasma properties are responsible for the decreased RBC aggregation observed in the neonates, but that their specific RBC properties do not affect it. However, the strength of interaction in the pRBC aggregates as a function of medium composition has not been tested. In our previous research, we described clinically relevant parameters, that is, the aggregate resistance to disaggregation by flow. With the help of a cell flow property analyzer (CFA), we can monitor RBC aggregation by direct visualization of its dynamics during